Sniping-
You always want a head shot when sniping, so if its possibly DO IT. Take your time (if you have time) and aim correctly. When the target is moving be sure to shoot ahead of the moving target, so you'll know you've hit em'. Don't aim for the head when the target is moving, unless you're a crack shot, don't take the chance of wasting your time, aim for the body. Also when sniping, when you use your scope and you shoot, hold the fire button to see if you hit them or else it will reload.
Assualt-
when you're shooting with and automatic, short burst with the weapon is more accurate. Just in case you didn't know, right click to magnify the shoot a little. Use your surroundings as protection, hide behind trees/rocks/buildings. When you come apon a tank (fucking noobs), always attack from the rear. It's way easier. Throw nades under the tank, its way more effectice than around the tank. MAKE SURE YOU TELL YOUR TEAMMATES WHEN YOU THROW NADES. If you're out of ammo switch gears with a dead person, just press G. Always use prone or crouch, it's very effective. It makes you harder to hit and easier to hide.
Anti-Tank-
This stradegy guide will be here soon as possible, dark will create this.
Engineer-
The engineer is just like the sniper, without the scope. The engineer is equiped with expacks, mines, colt, screwdriver, and a rifle. Use the expacks and mines to set up traps for vehicles, it will limit their moving space and it's sometimes a nice sneak attack. The rifle is very good, just like the sniper, try to get head shots. It's a very easy gun to control. Also when yours or your teammates vehicle is damage just fix it up with the screwdriver.
Medic-
Everyone needs the medic, which is why this is an important part of the game. The medic has basicly the same gun as assualt, but less powerful. Your team relies on the medic in cases of emergencies, so it would be best to stay with the pack but stay out of the way. Use the medic pack to heal you and your teammates, but do it in a safe place.