- Always use the Backburner
- Actually, only use the Backburner. The shotgun and axe are only there to make the other classes feel better.
- If you see an enemy, burn him til he's dead.
- If you see an enemy out of your flame range, run in a straight line toward him, spamming flames until he dies.
- If you died because you ran straight at a Soldier/Demo/Heavy, do absolutely nothing different. They are the problem, and are probably hacking.
- If your fellow teammates are on fire, ignore them. That's what medkits are for, and you need all the ammo you can get.
- The previous rule is especially true for Medics, since they can self-heal. Really, he'll be fine.
- Never attempt to reflect explosives/projectiles from yourself or your team. Again, ammo is precious.
- If you see a spy backstab your teammate, leave him alone. 9 times out of 10 he will get away, don't waste your ammo by pursuing him.
That's all I can think of atm, but I will add more and edit later as necessary.