Edit 2 years later: Why is this suddenly becoming popular. Up until now, it had no response, not even a view.

Enjoy some ♥♥♥♥♥♥ outdated tips, I guess.

SCOUT:

As a Scout, you are the fastest class (depending on your weapon) with this ability, be as annoying as possible (mic-spamming, chat-spamming or vote-spamming is nessecary) If your bad at getting kills as scout, just cause distractions to help your team. If you want to REALLY annoy everyone then try using Baby Faces Blaster and Frying Pan (Baby Faces Blaster for 2x speed and Frying Pan just because)

SOLDIER:

As Soldier, try not to accidently get in your own splash damage. You can do this by using your shotgun to attack close players and far away players with your rocket launcher. If you can't resist always going rocket launcher in any situation, use gunboats. If you use Market Gardener, practice timing when using it at the right time. While airborne, know the exact time to M1 to crit your prey.

PYRO:

As Pyro, one of the most helpful things is your airblast. Airblast does not cost too much ammo (depending on weapon) and can be helpful. When you see a friendly player on fire, use M2 to extinguish their flames. If your in a situation where your either fighting another pyro or an enemy is near a cliff, airblast them to push them away. A good pyro loadout is Degreaser, Flare Gun/Scorch Shot/Detonator and Axtinguisher. With Degreaser's fast weapon switch, put the enemy in flames first then switch to secondary and shoot them with that. Flaming players get critical hits with flare gun but mini crits with scorch/detonator. If you like playing 'Gay Spy' sneak up behind enemies and use degreaser to put them in flames, then quickly switch to axtinguisher and CHOP. This will to critical hits but only mini-crits when not in the back.

DEMOMAN

As Demoman, you can use your sticky bombs to put death traps in the cleverest places. For example (this one is funny until they figure out the trick) put your sticky bombs inside your intel. Since the intel can be shot threw, sticky bombs go threw it and makes them almost undetectable! This trick lasts unless the person is smart or already knows the trick. Like Soldier, try not getting in your own splash damage. Sticky Bomb and Grenade Launcher can both be used for far range. If your being chased, run behind a wall and plant sticky bombs. When the enemy comes around, use M2 to blow your sticky bombs up. If an enemy is far away, use grenade launcher or if you want them to not notice (like for example a wild pack of Snipers) use sticky bombs. Note: If you want more health as Demoman and you are good at melee weapons, use Eyelander. Eyelander starts you at 150 HP but if you get kills with the Eyelander, it gives you +15 Max HP per every kill in one life. Maximum health goes up to 210

HEAVY

As Heavy, don't think your the most overpowered class. Yes, minigun is good at close range but you don't have many far range weapons and the slowest speed. As Heavy, Medic is your loved wife (or husband) and you must protect eachother. Medic only has a slow health regeneration but this process from low health, to full takes long so you must help him. To help your Medic, use Sandvich. M2 with Sandvich in your hand to throw it on the ground with a plate. Anyone (even enemy players) can pick up your sandvich and use it as a health kit (except yourself, DARN YOU, VALVE!) Now lets do a test. Your looking straight at a Medic with a Sandvich, both of you have low health.
WHAT DO YOU DO?!
A. Eat Sandvich
B. Walk Away
C. Give Sandvich to Medic
D. Wait for Medic to heal on his own
If you answered C, you are correct. If you answered anything else, you're just a jerk to Medic. As Heavy, far away enemies are not the best to attack. Neither Minigun nor shotgun can do too much to enemies far away. Instead, just walk away from them or wait for them to come closer to you, then use minigun/shotgun. If you like playing 'Fat Spy' equip Holiday Punch. Use Holiday Punch to go behind enemies and punching them in the back. With this, you can either make them laugh forever or just use melee taunt to kill them.

ENGINEER

As Engineer, know what the common build order should be. First, build a Dispenser and level it up to atleast LvL 2. Once your dispenser is at LvL 2 or higher, build a sentry in a good spot where an enemy won't see it. If your dispenser is not close to your Sentry, move it close to it. Level your sentry up to 3 and do the same with your dispenser. If one is needed, add a teleporter. Teleporter entrances should be right outside/inside of spawn. Put your teleporter exit where it is most needed. (Examples: A walkway to control point, stairs down to intel, etc) DO NOT always stand on your teleporter or put it right next to your sentry. Put the teleporter close to your 'campout' Do this incase of Spies because they can use your teleporter when disguised. To tell if it is an enemy spy in disguise, walk up against them. If you go threw them, they aren't a spy. If you can't go threw them and they have a hitbox, they are an enemy spy. If you're too paranoid about spies, don't make a teleporter. If your building(s) are being sapped and your right infront of them, don't try removing the sappers, kill the source of the sappers. After the source is killed, repair your building(s) and remove the sappers. Ignore the 'Save the Endangered Spycrab' posters, you can kill all the spycrabs you want.

MEDIC

As Medic, look for 'cross' symbols on your screen. If the symbol is white, ignore it. If the symbol is red or reddish, go towards it. These symbols are your team (possibly spies) asking for healing. Use your medi-gun to heal players. NEVER be an offensive Medic. If you have no one to heal near you and you are being attacked by enemies, you can switch to bonesaw/syringe gun. As Medic, you heal yourself very slowly (about 3 health per second) so if your low on health, ask Heavies for sandviches or get med kits (or if you can defend yourself, sit in a corner and heal up but this is not recommended by me) Make sure you're not healing a Spy either, run into your team to see if they are Spies in disguise or not. If you can go threw them, they aren't a Spy but if you can't go threw them, they are a Spy. If they are a Spy, use Bonesaw to attack them.

SNIPER

As Sniper, always aim for the head. Aiming for the head on a full charge does about 450 dmg (depending on weapon) As Sniper, be alert of Spies and sneak attacks. Use Jarate to show hidden Spies and use Bushwacka to crit Jarate'd Spies. If your in a situation like an enemy is chasing you, you can attempt to snipe them while moving (if you find this difficuilt, use SMG)

SPY

As Spy, try not to run into enemies cloaked or disguised. If you are cloaked and an enemy runs into you, they can see you but if you're disguised, they can just feel your hitbox. If you're spy, don't hesitate. When your behind an enemy, backstab them, cloak and walk away to remain hidden. When your cloaked, don't feel like your a ghost. People can ever so slightly see your shadow when you're moving. As Spy, do not 'facestab' (stab someone in the face with your knife) this only does 40 damage and shows that you are a spy. Remember that when you attack as Spy you will un-disguise yourself. While cloaked, you cannot attack. As Spy, you can take enemy teleporters but make sure no one is standing on the teleporter if you teleport after them. If you teleport when an enemy is standing on the opposite teleporter, when you teleport the enemy will die (enemies can do this to you too) If enemies see you teleport and kill whoever was standing on the teleporter, they will know you are a Spy (unless they are just stupid) If Engineers are off-guard on their building(s) use sapper and click M1 on their building(s) If the Engineer comes to repair his building(s), look innocent and while they repair, backstab.