Just like you cannot play a bass guitar without actually having a bass guitar, strings, and an amplifier, you can't play Left 4 Dead 2 like an expert without having some gear.

• Computer
  
  You will need a desktop PC to play the game like an expert. Nothing fancy, but it should have a decent frame-rate and good sound. Sure, you can play on a laptop, but it better be one of those gaming laptops, or you won't get very far. Playing on a console is also possible, but the controller is inferior to keyboard and mouse.
  
  
• Keyboard & Mouse
  
  Stay away from wireless mice and keyboards. They are comfortable, but they introduce lag. You want your lag to be the smallest possible, and you don't want your batteries to run out in the middle of that important game.
  
  
• Keyboard
  
  Avoid absolutely cheapest keyboards such as A4Tech, Genius, Trust, etc. The reason they are cheap is that they don't work well when you press many keys at once. You don't need to spend a fortune on a keyboard -- even a simple Logitech K120[www.logitech.com] will work just fine.
  
  
• Mouse
  
  Avoid absolutely cheapest mice such as A4Tech, Genius, Trust, etc unless you want jerky movement and buttons which don't fire when you need them most. At a minimum, get yourself a decent Logitech mouse. Depending on the mouse design optical sensor can be sensitive to external light, and it doesn't work well on all surfaces so some people (myself included) prefer laser sensors. In my opinion, even the cheapest laser mouse is better than optical mouse nowadays. In any case, there is plenty of choice, and you should do your homework to find a mouse that suits you well.
  
  
• Headset
  
  You can play using speakers and desktop microphone, but you shouldn't and here is why. First, you will have a harder time hearing Special Infected and determining the direction of the threat. Second, when you speak everyone will be deafened by the sound coming from your speakers.
  
  Therefore, headset (or a pair of headphones with a desktop microphone) is a must if you want to play like an expert. Get something decent with wires which don't feel too thin or stiff. Last thing you want is for everyone to hear buzz every time you speak. I prefer over the ear, open-back headphones because they are more comfortable for longer playing sessions.
  
  It goes without saying that wireless should be avoided, and that you should configure voice in the game to Push To Talk mode and use it only when necessary.
  
  
• Sound card (optional)
  
  Onboard sound cards are decent enough for most users nowadays. However, if you want to have a slight advantage, then get a dedicated sound card which can handle EAX effects and positional audio in hardware. Creative sound cards are a good (albeit expensive) choice, for example SoundBlaster Zx[us.creative.com]. With that one you will also get a really good noise-cancelling microphone.
  
  
• Internet (D'oh!)
  
  To play multi-player games you need to have a decent broadband Internet connection and your computer must be connected to the network using cable, not Wi-Fi. Much more important than the download speed of your Internet connection are latency and jitter.
  
  Latency (a.k.a. ping or lag) is the time (usually measured in milliseconds) it takes for a request from your computer to reach the game server and for your computer to receive the response. The lower the number, the smoother the gameplay will be for you. Latency will depend on the distance (in network and/or geographic terms) of the server and your computer. For non-professional gaming acceptable is up to 65 ms -- anything over that number requires you to adjust your aim ahead to compensate. If everyone on the team has high latency on some dedicated server then vote to go back to lobby and try to find another server, or use the server browser from the console to manually pick one with low latency.
  
  The other term (jitter) denotes how stable your connection is. It should be low to non-existent. Look at the jitter as a deviation of latency from the usual number. If your ping starts with 35 ms, but goes to 70 ms, or even 667 ms then you have jitter.
  
  Jitter can be temporary, for example caused by someone in your house downloading or uploading stuff at full speed while you play, or permanent -- you could have a bad router or a poor cable modem signal, or your ISP has oversold their capacity and the problem is in their network.
  
  In any case, with high jitter it is impossible to play multi-player because all characters on screen will appear to be teleporting around, and you won't be able to compensate for random lag when aiming thus increasing the risk to incapacitate your own teammates. What is worse, you will also appear like you are teleporting to your team and they will orten accidentaly incapacitate you as well so it is better not to play until you fix it.
  
  If your ISP has provided you with a router it is usually a crappy low-powered one, especially if it also has Wi-Fi on it. The best option is to buy your own router (for just $100 you can get a high-performance Gigabit router such as Ubiquiti EdgeRouter Lite), and invest some time into configuring it properly. However, for that to work, your cable (or DSL) modem must support bridge (in addition to NAT) mode -- in other words, your ISP should let you assign the public IP to your own router, so check with your ISP whether that is possible before purchasing anything.

Before you start playing, you might want to do some tweaks to your system. Here is what I recommend.

• Keyboard
  
  Like in every other game Left 4 Dead 2 action keys can be customized. Sure you can accept the default WASD layout, but if that feels clunky you can also configure your own layout. Spending some time in single-player game to find optimal key layout for yourself may help you play better. Also, make sure to enable developer console because you never know when you might need it.
  
  
• Mouse
  
  In Windows, disable Enhance pointer precision option in Mouse section of the Control Panel. If your mouse comes with dedicated settings application or you are on a Mac look into how to disable mouse acceleration. You want your mouse movement to be uniform. If your mouse has the ability to adjust the USB polling rate[blog.codinghorror.com], set the highest possible rate.
  
  In the game under OPTIONS then under KEYBOARD/MOUSE set the following:
  
  
  • MOUSE FILTER to Disabled
    
  • RAW MOUSE INPUT to Enabled
    
  • MOUSE ACCELERATION to Disabled
  
  You will also notice an option MOUSE SENSITIVITY -- set this to get the turning speed you are comfortable with. Note that with high DPI settings on the mouse you will have to reduce this almost all the way down. I am using Logitech G500s at 900 DPI, your mileage might vary.
  
  Note that I am not a professional player and what I say above is my personal preference which may or may not align with what is considered "proper" mouse settings. Feel free to read other guides that go into more details on this topic, but make sure to try out different settings and find ones that work for you. There is no point in using my or anyone else's settings if your aim sucks with them.
  
  
• Audio
  
  The only important thing is to set the audio quality to high. I also turn in-game music off so it's easier to hear Special Infected. I am using a stereo setup (2 speakers) even though I am using stereo headphones, and that is what I recommend. For me that gives the best sound clarity in game. I prefer good quality stereo headphones to average quality multi-channel (5.1 or 7.1) headphones.
  
  
• Video
  
  With a good video card you can set everything to the highest possible quality and still have 200+ frames per second in the game. One important thing to reduce lag is to set the lowest possible number of prerendered frames in your video card control panel. I play with VSYNC set to Disabled, you can play with Enabled or Disabled, or if you have one of those fancy, expensive GSYNC monitors you can enjoy even less lag at the expense of color quality and terrible viewing angles.
  
  
• Interpolation
  
  This is the subject of heated debates. If you want details, look up interpolation (a.k.a. lerp) guides. The settings I am using are as follows:
  
  cl_interp 0.067 cl_interp_ratio 0
  I find those settings the lowest I can use without in-game movement getting choppy when there is a lot of action on the screen. You can type those two commands by hand into the developer console each time you start the game, or you can just edit your autoexec.cfg and put them there. How to do that is out of scope of this guide.

If you are reading this guide chances are you already have quite a few hours spent in the game. This guide won't explain differences between weapons or zombie types, there are many other guides out there already which do just that. Instead, this guide will be focused on helping you become a better player by improving your knowledge of the game environment, your situational awareness, and teach you how to manage your priorities.

The first important thing is to memorize the game maps. You need to learn the following:

• Direction
  
  It goes without saying that you should know which way to go at all times so familiarize yourself with all the maps, even if it means playing them on Easy so you can wander around and explore every nook and cranny until you learn the map inside and out.
  
  
• Crescendo Events
  
  Each map has specific crescendo event spots[left4dead.wikia.com]. You need to know where they are and always be prepared when you approach them.
  
  
• Infected Ladders
  
  They are invisible to Survivors and there are two ways to learn where they are in each map. The tedious way is to observe where zombies are climbing during horde attacks. The easiest way is to play some Versus as a Special Infected and look around the map. It is important to memorize where Infected Ladders are located -- once you know that you will never choose a bad spot to defend yourself again.
  
  Of course, if you join a Versus match and just wander around staring at the walls you will get kicked so instead get Rayman1103's Mutation Mod which will enable you to play Versus with bots -- you can look around the map as much as you want without ruining someone else's game.
  
  
• Danger Spots
  
  There are certain places on the map which are dangerous to linger around. Just like in real life you should stay away from the ledges, open windows, fires, large bodies of water, and large, heavy objects such as cars, trash containers, and forklifts. Charger, Jockey, or a Smoker can perform an instant kill if they cause you to fall from height or into the water/fire, and Tank can kill you by punching cars, trash containers and forklifts at you or punching you over the ledge.
  
  
• Choke points
  
  A choke point[en.wikipedia.org] is the narrow spot which is easy to defend even when you are heavily outnumbered. You should learn the maps such that at every moment you know the closest choke point and are able to automatically fall back to it in case of a large horde. Instead of standing in the middle of the open space, move to a corner, to a corridor, or behind a door frame to reduce the attack surface.
  
  When in a corridor or in a room with two entry points make sure someone on the team is watching the other entrance. The most important Special Infected to watch for is a Spitter. As much as a choke point gives you an advantage by preventing the zombies from coming in and flanking you, it will also prevent you from rushing out so if you get spat on you will go down.
  
  
• High ground
  
  The high ground[en.wikipedia.org] is where you always want to be when in combat. A perfect example of a high ground area is the area immediately to the right of the safe house in Blood Harvest chapter The Train Station. Most people I played this chapter with always go straight towards the barn by following the walk path and they get swarmed by the horde in the open. Next time you play that chapter turn right when you exit the safe house and then go up the hill by following the right wall -- you will see the advantage of being on a high ground for yourself.

The presence of the A.I. Director[left4dead.wikia.com] makes Left 4 Dead 2 a game of situational awareness. No matter how skilled you are there is always an element of chance -- just like you can have a streak of bad luck in poker you can have Director punish you for not paying attention.

I cannot stress this enough -- you must be aware of all possible threats.

That Hunter which just spawned? Can it flank us? Is that Spitter close enough to make a combo with the Hunter? Is that low growl behind the wall a Tank? How far back is that Smoker? How much time passed since we had the last horde? If I set the Witch on fire will I have enough space without obstacles (including potential horde) to outrun her?

You need to know the answer to those questions at all times, and this is where experience comes to play. You learn those things by having enough in-game hours, just like you learn playing guitar by practicing at least an hour a day.

If you are naturally poor at multi-tasking, this game is not for you -- those pesky zombies closing up on you will easily distract you from the more serious threats lurking in shadows waiting for the right moment to strike. Many players think that just having good aim is enough to play this game. That can't be further from the truth. The aim is important, but not the most important. The most important are situational awareness and threat prioritization. Aim can always be improved by practicing, but the other two rely on your common sense. If you lack that, then no amount of practice will help you.

This section will teach you how to determine threat priority so you can minimize the damage to your team. To keep it simple I will present it with several examples in the form of a quiz.

Q1:

If out of 4 Survivors you are the only one free, and the other 3 are pinned at the same time by:

• Smoker
  
• Hunter
  
• Charger or a Jockey

In what order do you try to save them?

A1:

• The one who is black and white (if any)
  
• The one pinned by Hunter if Hunter is on fire or the one pinned by Smoker if they are hanging in the air on its tongue
  
• The one who is pinned by Charger or a Jockey

Q2:

If out of 4 Survivors you are the only one on your feet, 1 is incapacitated and is about to die, 2 are dead, but they have spawned in the closet nearby, and there is a danger present (Special Infected around the corner) what will you do first?

• Try to eliminate danger
  
• Try to revive incapacitated teammate
  
• Try to open the closet

A2:

If the closet is within reach and there is no risk to get pinned by the Special Infected open the closet first, then help incapacitated player while the other 2 players watch your back.

Some would argue to revive incapacitated player first but if you do so, you will be vulnerable for several seconds, and they will be of little help with further threats with their health in red and possibly having to reload compared to other 2 players with 50 HP each and full magazines.

Q3:

If out of 4 Survivors you are the only one on your feet, 1 is dead on the ground, 2 are incapacitated, there is a danger present (Special Infected around the corner) and you have a defibrilator what will you do first:

• Try to eliminate danger
  
• Try to revive incapacitated teammates
  
• Try to revive dead teammate

A3:

Revive a dead teammate of course unless one of the other two is on a verge of death in which case you try to save them first. Reviving a dead teammate takes as long as reviving an incapacitated one. The advantage of using defibrilator is that you will get 1 player with 50 HP instead of 1 with their health in red who can be taken down by a single Jockey scratch.

How you will fight the Tank mostly depends on the location where you encounter it. The Tank has 8,000 HP in Expert mode -- compared to the health of the fully healed player (80 HP) that is 100 times more, so it requires some teamwork to take him down.

As long as the number of non-incapacitated survivors is greater than 1, the Tank will chase the one who is dealing him the most damage, while the others will be ignored unless directly in the way. This is a simple fact which should always be used to your advantage -- it comes very handy when someone is incapacitated or when you are fighting the Tank in close quarters.

To fight the Tank in close quarters you should split into two teams -- let's call them Team A and Team B. The strategy, which for the lack of better name I will call "pendulum", consists of 10 easy to follow steps:

1. Team A immediately opens fire at the Tank
2. The Tank starts chasing Team A
3. Team B flanks the Tank (the goal is to be on the opposite side from Team A)
4. As the Tank starts gaining on Team A, they cease fire and hide behind obstacles
5. Team B opens fire at the Tank
6. The Tank switches targets, and starts chasing Team B
7. As the Tank starts gaining on Team B, they cease fire and hide behind obstacles
8. Team A opens fire at the Tank
9. The Tank switches targets, and starts chasing Team A
10. Repeat from step 4 until the Tank is dead

Q1: How do I become the Tank's target?
A1: Deal the most damage to the Tank. Setting him on fire and shooting him usually does it.

Q2: Is there any other way of becoming the Tank's target?
A2: Yes, come behind the Tank and melee it (or just shove it if you don't have a melee weapon).

Q3: I am shooting the Tank and it still won't start chasing me, what gives?
A3: In order for that to work, the rest of the team must cooperate and cease fire temporarily.

Q4: Wait... why would I even want to become the Tank's target?!?
A4: There are many reasons, see the next section for examples.

Q5: Help! The Tank is chasing me! How do I shake it off?
A5: Cease fire, and gain enough distance so it starts chasing someone else who is shooting at him.

Again, situational awareness is the key here, and a few examples of in-game situations should explain why it is so important.

Let's say you have two incapacitated team members, and in order to save them one of you gets the Tank's attention as described above, and starts luring him away so the other one can revive them. Now the question is, should the other one try to revive them? Well it depends...

Is there a horde present around them? If yes, then do not try to revive. Better way is to provide cover fire for the incapacitated and to pick out any stray zombies chasing after the other teammate who is playing a bait for the Tank.

Are there Special Infected around? If yes, pick them out first. If no SI and no horde, then try to revive the teammates. But... (and this "but" is a big one) be aware of the other player who will be fighting the Tank alone for several seconds while you are reviving them.

Does the other player (a.k.a "Tank Bait") have enough space behind them to keep the distance while they are leading the Tank away from you? If they are getting cornered by the Tank, then forget the reviving and start shooting the Tank immediately until it starts coming back towards you.

The reason is simple -- if you don't help the other player the Tank will incapacitate them, and next thing you know you will have to fight it alone. If you survive you will have 2 dead teammates and one injured instead of just 2 dead.

This section could as well be titled The Ethics of playing Left 4 Dead 2.

It is a simple list of (common sense) rules and in-game behavior tips which make a difference between people wanting to play with you or wanting to kill or kick you.

1. By all means, and at all times pay attention to the game. If you get a phone call and you simply must answer, or if you have some other real-life emergency while playing please at least select TAKE A BREAK from the main menu and say you are away from keyboard (AFK) so you don't hold up the whole team, and if you know it's going to take a while it is better to say you have to go and exit the game alltogether.

2. Learn English. Even if you hate those imperialistic bastards, most people know English and you will have easier time playing the game with other people.

3. Do not play Multi-Player Expert with less than 100 hours in game. Try finishing all campaigns on Single-Player Expert with bots first. Bonus points if all bots are alive in the rescue vehicle. Start Multi-Player on Advanced, then move to Expert as you gain experience in interacting with other players.

4. Never take more than one medkit unless there are spares left. Many players consider this rude, myself included. There are 4 players and 4 medkits on the beginning of each chapter. You are not worth 2 players, and even if you were, everyone deserves equal starting point. Sometimes people will immediately kick you for taking a second kit, and sometimes they will protest it by refusing to share items with you and leaving you to die when you get pinned by an S.I.

5. If someone is black and white, you are in green but not at full health, you have medkit, and they have pills, heal them and then ask them to give you their pills. That way you will both have maxed out health. Sharing is caring. That player limping at the back? Give them pills if you can spare so they don't drag the team down with their slowness.

6. Do not open spawn doors unless you are playing Realism Expert. You never know when you might need them.

7. If someone dies and there is spawn nearby do not take their stuff unless you are the last one alive and you are black and white. Even then, take only temporary health because if you get pinned by an S.I. there is no difference between pills and a medkit -- you will die either way and if you don't you will still have a spare medkit to use later. Take their weapon only if you are last one alive and out of ammo. As a general rule, if you need stuff the polite thing is to ask first. Most people will let you have their stuff. The only time when you don't have to ask is when they die close to a safe house and there are no spawns or defibrilators left.

8. If there is a Tank in a tight space such as corridor split in two groups on the opposite sides of the Tank if possible and pull it back and forth by alternating between shooting at it and ceasing fire while the other half of the team is shooting at it.

9. If a teammate is down and there is a Tank passing directly over it CEASE FIRE so the Tank doesn't kill them. If you are close to the Tank run up behind it and melee it to distract it from the incapacitated teammate and get it to chase you.

10. If there is a Tank do not throw bile on it, especially not in levels with Uncommon Infected (riot cops, construction workers). The only exception to this rule is if you have seen the Tank (e.g. his hand is poking around the corner) but he hasn't seen you yet. Bile him without him seeing you, step out of the way of the horde and watch him get killed.

Occasionaly someone will join your game, kill your whole team, vote to restart, and leave.

The best way to deal with team killers is to:

• Press Shift+Tab when it happens (to activate Steam Overlay)
  
• Click on VIEW PLAYERS button
  
• Click on RECENT GAMES tab
  
• Click on the Profile link next to the offender's name and avatar
  
• Click on More button on their profile top right
  
• From the drop-down menu select Block All Communication
  
• Click on Yes, block them button

From that point onwards they will not be able to join your game anymore.

I hope you find this guide useful. Thanks for reading, enjoy the game!