Setting the other team on fire is just a code phrase for “giving the other team more uber charges,” which is what makes the pyro the worst class in the game.
That’s assuming that the other team has a medic, and that the pyro doesn’t make a point of finishing off the medic (if any) in addition to burning people in general. I’m new at this, but I make a point of gunning for any medic I see.
Which part of “kamikaze run” did you not understand? 
Seriously, take Covered_In_Bees!'s advice and don’t stick to the Pyro. She’ll want to either mix it up in a large group or sneak around the back way to pick off unsuspecting single players. You’ll die quickly in the first case and in the second case the Pyro probably won’t appreciate a glowing stream blowing her cover.
“Target the Medic first” is good advice no matter what class you’re playing. They can’t give an Über if they’re dead.
Pretty much. My Pyro also carries a Back Scratcher which gives +50% from health packs but -75% Medic healing. It’s almost always a benefit though since it’s so rare that I have a medic bothering with me and so common that I’m grabbing health packs on my own to stay in the game.
Oh, one more piece of advice for medics: HEAL SCOUTS TOO!
Scout, when played properly, is one of the most powerful classes in the game. However, they are going to get damaged and even minimal damage to other classes hurts scouts a lot, so they will need heals somewhat more frequently.
Keeping your scouts overhealed at the very least means they will be able to survive 1v1 scout encounters, which will of course keep enemy scouts from harrassing you, the medic.
You know what pisses me off as a Medic? When a Scout, in need of healing, runs right past me.
You know what pisses me off as a Pyro? When a Scout, on fire, runs right past me.
Actually, both are true for any class, but the Scout is the fastest class in the game. Gotta give us a chance to catch up to you, dude.
I’ve had the game since it came out. I love it. Yet I still haven’t been able to use the scout well. How do you play it properly?
Scout scares me. It seems to be based primarily around the twitchy, back-n-forth spastic gameplay I’m too old to get a handle on. That’s no ding on scouts but an assessment of my own limitations.
If you’re not the twitch gamer type, the Scout class is pretty much forever closed to you. They’re monstrously powerful with their ability to run down or away from anyone while still delivering some of the highest damage output in the game, but it’s totally reliant on being able to hit targets accurately while erratically maneuvering in three dimensions. The scout has the capability to win every 1v1 duel handily and in general can do the Spy’s job better than the Spy can.
The basic Scout concept is simple: get in when nobody who can bother you is looking, get a few good meaty shotgun hits in, dodge return fire and get out - reload, wash, rinse, repeat. Actually executing it in practice…not so simple.
As for the pyro, it’s a good newbie class in theory because just running forward at enemies holding the flamethrower open is going to be a threat to newer players, the weaker classes or distracted enemies. In your average game, it’s likely to do some damage while not requiring much in the way of execution competence. Yay!
The problem is that I’d never recommend pyro for a new player because, frankly, the pyro just isn’t very good: Pyro is close-range, but can only outrun the people who are very good at killing pyros, so you need to know the maps and player responses. The pyro is the only class that basically requires nonstandard weapons to open up their gameplay to be competitive in flexibility or damage output. The only real bonus pyro brings to their team is the airblast, which is not newbie friendly whatsoever.
Worst of all from a new player perspective, though, is that pyro success is deceptive. You’ll see kill and assist messages pop up from afterburn, but many of those probably have little to do with what you actually did to the target, and is just the game scoring being overly generous to you. Some of the best things you can do as pyro will grant you no points at all. If you’re learning the game as pyro, you might be taking the wrong messages away. Worst case scenario, you could even be helping the enemy team and not realizing it.
“some of the best things you can do as a pyro will grant you no points at all”
Like what, aside from putting out fires?
How about the sniper, what’s the basic sniper concept?
Pyros can do hit and run burnings. Fire does extended damage to targets, and is useful when someone on your side is engaged in combat with an enemy. However, kill assists don’t net you points in-game (other than as a medic who is healing). (However, they do earn you points in your metascore.) If you burn and run, your ally will likely finish the enemy off. Also, burning targets tend to try to get themselves put out which may make them run away from combat thus ruining their plans. Plus, the pyro is one of the best spy checkers out there with fire. Especially since a burning spy can’t use the death faking power effectively.
Also, airblasting uber medics is a great tactic since you can break up the uber. You get no points for this either.
Also, airblasting to deflect soldier rockets won’t get you points unless you can aim it to take the soldier or another enemy out in the process. But frequently the deflection alone is very useful, especially if you have allies clustered near you because you prevent both a direct hit on a target and splash damage to the cluster.
This list is far from exhaustive, but its a start.
Stand still and let my Pyro char you as you’re staring off in the other direction. If I’m playing a sniper, my primary function is to give the enemy snipers something to do :dubious:
Snipers can hit the right mouse button and zoom in with a scope. When they do, others can see a blue or red dot moving about, Hollywood style. Body shots are damaging, headshots crippling or insta-death depending on the target. Good for taking out Medics, softening targets like Heavys or knocking out sentry guns from a safe distance. Plus, of course, general people killin’.
The rifle has a very long range and a slow reload time. When threatened up close, switch to your submachine gun or knife. Snipers are favorite targets for Spies and Pyros since the scope severely limits your view of the world around you and the whole “sniping” thing has you staying still. People have a pretty good idea where Snipers usually hide out on the more common maps so once a Spy/Pyro gets behind enemy lines, it’s Sniper-hunting time. Snipers can get a back item (shield) which will absorb a backstab for at least a little warning.
I believe if you airblast someone off a cliff, it counts as a suicide for them. Similarly, airblasting a Medic off his Heavy or stickies off the control point won’t give you any points.
Pyros are also useful for detecting enemy spies; just give everyone with the same color as you a quick blast of flame. The general disruption to the enemy team that you can do as a Pyro can be enormously helpful to your team. Due to my habit of sneaking around the back, I’ll often find myself dead behind enemy lines, but I’ll still call out intel to my team.
Firing exploding flares (Detonator) into a crowd and setting them on fire from a distance tends to make people act stupid which can be amusing. It’s not exactly subtle though so someone usually ruins your fun in a hurry if you don’t move along.
Ah, yes. The Sniper’s back shield doesn’t protect against fire. Even if I’m across the map, I can set a Sniper alight with my flare gun; it won’t kill them but will make them think there’s a Pyro behind them. Great fun!
I found uses for airblasting very quickly, including messing with Medics. I disrupted several attempts to use an ubered pair to take out a crucial sentry gun that way. (Though I think the medic’s partner was also screwing up the uber occasionally, somehow.) I also used it for area denial on control points (especially good on points that are on small, elevated platforms) and for clearing stickies. Knocking people away from dispensers isn’t bad, either.
I didn’t quite get the knack of deflecting rockets, though I tried. I managed to knock a few off course, but I didn’t blow up any enemies with them.
Putting out fires as a Pyro does give you points. It gives you one full point for each extinguished enemy.
And thanks to the generous and heroic SenorBeef when I joined the SDMB server last night, so does mine! 
This is not a particularly easy game to snipe in. You need to be extremely fast and accurate because most classes move so quickly. The only really easy shots are engineers who are building or repairing, sentry guns, heavies firing their miniguns, other snipers, and newbies who hold still for too long. Beyond that, remember that one fully-charged body shot will kill a sniper, a medic, an engineer, a spy, or a scout. Other classes need a headshot.
However, in most online games there are way too many people who just love to play sniper. It’s not uncommon to see a quarter or a third of a team playing sniper, and that’s usually a recipe for failure. It’s not that they’re bad at it (they’re often quite good) but snipers aren’t very flexible or fast. Like spies, often one per team is often enough. You don’t do that much damage, but you force the other team to react to you, act in a paranoid way, and reduce their effectiveness. For that reason, I rarely play sniper; there’s no need.
How about the heavy, any basic concept or trick to him?