I'm not going to be long-winded about this
If you're reading this than you are either new to the Chaotic, Hat-Themed Game of Team Fortress 2.
Or you just want some pointers on the least appreciated (yet most demanded) Class in said Chaotic War-Themed Hat Simulator

Let's get what the Medic was "born to do" outta the way with the General Rules for Medical Application and Distribution of Medigun Healz

1: You need to know that ALL Classes should be healed, none of that "Heavies (Or Demos or whatever the Hell else) are the only ones that deserve healing" BS, The more of your friends (teammates, etc.) you heal, the faster you build an UberCharge (Provided you live long enough to pop one, see Combat for tips). With that in mind, also factor in the age-old tradition of First-Aid. Essentially heal whoever has the lowest amount of health within your current area until they are fully healed or someone else nearby is dangerously low

2: Heal other Medics.
In the astronomically rare event there is another Medic on your team, if their health gets low, treat them like any other class and heal them up. While all Classes deserve healing, Medics always take top priority, and as a Medic you can keep your teammates alive and well without running to the next health pack where they can be picked off easily.

3: Don't Fondle Your Patients / Don't Overextend
A double lesson here. Don't get too close to your patient as Pyros can burn you as well as who you're healing (Personal Experience), the Medigun has a longer reach than you think. That being said also DON'T "Overextend". What's that you may ask, well it essentially means don't get too far from your patient and don't try to phase it through a wall, that doesn't work either, just be careful in the field as not only can fire get you, but splash damage from explosions and stray bullets

4: Never be Stingy with an Uber
An Ubercharge is the One Ring to your Gollum, and takes forever to charge up on stock Medigun/Reskins. I bet you also didn't know you could also use an Uber on your own to save your skin from that one pesky Scout that has you on the ropes, you can! As long as it keeps you alive then go for it, less time out of the field for you. I also want to throw in that different Ubers are useful for different situations, if you have the Kritzkrieg, do NOT pop it in a Sentry Nest, Machines are not affected by Criticals (Unless it's MvM). Just a warning guys...

Now on to the Medic's applications for Self-Defense/Offense
And no i don't mean a Full-Fledged Combat Medic, just one that can defend themselves if the need arises

Syringe Gun: You can use whatever your heart desires for any of these weapons, but I use the Blutsauger for survivability purposes, as a registered hit on any enemy heals you +3 Health

Bonesaw: The Bonesaw is actually the best stock weapon for criticals in the game (I think), but you can use the Ubersaw, Amputator, Etc. I use the standard edition Bonesaw though

Practical Uses:
Say a Pyro is charging towards you, looking to make you into a German BarBeQue, and you have the Blutsauger... The Pyro isn't the smartest since you can easily heal back any damage the burning does if you keep a steady stream of needles flying into their facehole, or bodyhole... It doesn't really matter
With the Crusader's Crossbow, it's mainly used for more of a 'Drive-By" Healing Method, a quick shot or two and they're good to go, allowing you to quickly reach others in a much more dire situation, but it's also got a use in combat. It's not grand but it'll do in a pinch for shooing away the scout or sniper trying to pick you off

What to Avoid:
Basically Avoid any Class that is serving as your Predator, mainly Scouts, Snipers, Spies, and the Occasional Pyro or Soldier. To protect yourself from these threats, try convincing one of your teammates to guard you. More specific instances are mainly a Pyro for Scouts and Spies, the best defense from a Sniper, is ironically another Aussie Assassin. But in any case, try to keep moving around the map like a scout would, it's much harder to kill a moving target than someone standing still (More Personal EXP)

A few other Quick Tips I neglected to mention earlier are listed Below

Target Evaluation:
In TF2, it's rather shameful but you can more or less Racially Profile Players based on the Cosmetics they are wearing. For example, a Scout wearing an unpainted Gibus and Pyrovision (The F2P Holy Grail) should be muuuuuch easier to fight against than one wearing a Flak Jack and Deus Specs, and so on and so forth for the rest of the classes. Also take note of how Flashy the cosmetics they're wearing are, if they don't really stand out (but still show that they have experience), be sure to watch out for a sneak attack (Helpful little Tip). Also, never try to take on 2 players at once, especially a combo like a Soldier and Pyro. You need to know when to Run as a Medic, ESPECIALLY with an Uber ready.

Take Advantage of the Environment:
In other words "Learn the Maps". If you know where Health and Ammo SHOULD be and are low on either or both, Run like Three Pyros are after you to those pickups and continue the fight. Engineers are your friends as well, Sentry nests should always have at least One Dispenser to replenish your Health and Syringes, so be sure to keep those locations in mind as well. Watch out for Snipers, Spies, and Ubered Power Classes (Soldier, Demo, Heavy, even Pyro) though.

And there you have it, my complete Guide on how to Play Medic Pretty Sorta Okay-Ish, I wish you good luck in your Medical Endeavors

Stay Classy San Diego

Signed,
Fedora_Core {Corey}