In general, you can take what you’ve learned from playing Team Fortress 2 and translate it to Team Fortress Classic. They are the same 9 classes after all, and they have mostly the same loadouts, just with more shotguns. Some things will throw you for curveballs (I wrote a pretty extensive guide here) but in general you can guess what each class is about.
TF2 will not prepare you in any way to start playing the TFC Combat Medic. Especially if you’ve played the TF2 Medic. Playing the combat medic like this will instantly label you as a TF2 immigrant who has never touched the game before. I was one of those once, but I persevered and now I consider myself a proficient TFC medic. Note that anyone who played TFC in its heyday could educate you better then me, but here’s what I’ve learned:
1) Your primary job is not to heal your teammates. This gets its own bullet. While you have a medkit, and Valve intended this to be your job, the metagame has moved far past this. The medkit suffers from abysmal hit detection, it doesn’t restore armor, and respawn is instant, so death isn’t really a big deal in TFC. We’ll cover your actual job in the next bullet; for now, just remember that you shouldn’t stick your neck out to save teammates, there are better things for you to be doing. (Of course, heal teammates if you get an appropriate opportunity, and overheal everyone while stuck in setup time, but keep the map objectives in mind first.)
2) Your primary job is to capture flags. As I mentioned in my memoir to Team Fortress Classic, it is far more flag-based than TF2. In general, a team wins by being able to control the map’s flags better than the opposing team. Scouts and Medics are known as “flagrunners”; they use their speed and mobility to bypass enemy lines, nailguns to defeat enemy sentries defending the flag, and dodging ability to zip away with the flag. The Concussion Grenade is the most important weapon in your arsenal; it’ll launch you through the air in a wide arc dependent on your distance from the epicenter. Learning how to manipulate its nuances is vital to playing TFC Medic.
Your other weapons were designed for self-defense, use them in that way. Never worry about killing an enemy; you just have to keep them at bay long enough for your next conc to finish cooking, and then you’ll be gone. Your frag grenades and nailgun can make short work of enemy sentries, one of your biggest impediments as they’ll always be loitering around the flag spawn. On that note, let’s go over your loadout.
3) Know the tools at your disposal. TFC classes have way more weapons on hand than TF2 players may be comfortable with. In most cases, you should run around with your Super Shotgun out, but here’s a breakdown on all of them, ordered by default key.
1 – Medkit. While certainly more useful than most other melee weapons, its hit detection makes any clutch uses in combat unreliable. (It also deals zero damage to enemy buildings.) If you do land a hit on an enemy, the resulting infection deals great DoT that can only be stopped by enemy medics or death, so it can either aid your getaway or ensure they’re softer when you return for the next flag. In practice, I rarely use it.
2 – The shotgun. It is identical in every way to the super shotgun below, except it fires less pellets. So yeah, just use the super shotgun all the time. This gun is for when you’ve run out of super shotgun ammo or clip.
3 – The super shotgun. All things considered, your primary. Fight opponents, lay covering fire, it deals respectable damage and is particularly good if combined with dodging and maneuverability. Make sure to get good with using this gun while concussed, since you’ll be concussed a lot.
4 – The Super Nailgun. It deals more DPS than any other nailgun in the game, firing a stream of nails in a straight line unaffected by gravity. Great against sentries and unmoving targets like snipers. It’s also no slouch in narrow corridors, where the enemy is less capable of dodging the wave of nails.
F – Frag grenade. Great against pretty much anything in the game, but especially sentries. Main thing to beware of is that 4 second fuse, more than enough time for the enemy to prepare their own grenade. Like with any class, its important to get good with the most famous weapon in TFC.
G – The concussion grenade. We’ve already gone over this, you can fly across the map, chain them with other conc grenades, all sorts of tricks are possible. It can also be used for the function Valve intended when they made it; hitting enemies and completely messing their aim up.
One of the things I’m trying to establish is that you are very versatile. You have speed, health regen, medium armor, and your weapons can pack a punch. You usually have an option or two in any situation, you’re actually more of a jack-of-all-trades than any class in TF2. It’s just a matter of playing the class and figuring out what you’re capable of. You can’t get this experience with TF2, so I urge you to give it a shot.