How to contact server admins in Battlefield Bad Company 2

• Play to the strengths of the class you're playing. These rules bend a lot but you'll learn that with experience.
  • Assault - Drop ammo packs near teammates. Pick off guys at medium distance. Long distance works well too but that's best effective on defense. Shoot your grenade launcher at bunched up enemies.
  • Engineer - Repair friendly vehicles, blow up enemy vehicles. Shoot vehicles with the RPG-7, shoot soldiers with the Carl-Gustav. The CG does less damage but the rocket travels faster and has a wider damage radius. Your SMG is best used at close range.
    • Any class can use the tracer dart, but here's how to lock onto it. Once it's on the vehicle, look down the sight of your RPG at the red blinking square in the direction of the beacon. Once it stop blinking, you have about two seconds to shoot. You can even shoot straight in the air to curve it around buildings and terrain. You don't need line of sight to lock on. You do not need to stay aiming until it hits. Once it's locked, it's locked, but the next time you shoot you'll need to lock again.
  • Medic - Drop med kits near teammates. Revive dead teammates with your paddles (they appear as lightning bolts on the map and your HUD). Your light machine gun doesn't do much more damage than other guns but you have quite a bit more ammo per magazine. Best for medium distances.
  • Recon - Throw your motion mines, this reveals enemies in a small area as blips on you and your teammates maps. Use C4 to blow up vehicles that get too close (you can't throw them very far) and use mortar strikes to disperse camping enemies. Mortar strikes don't damage the M-Coms in Rush, but C4 does. Motion mines can also be an excellent offensive tool for rushing a building.
• Spot. Push the spot button like you're on crack. (Back on 360, Select on PS3, Q on PC) This puts a blip over the enemies' heads and on the map. This can also be very useful if visibility is low due to smoke or if you're not used to iron sights, since the blip is drawn on top of your weapon.
• Don't drive vehicles until you have some experience. This includes the UAV. It's fun, but you're not as invulnerable as you may feel and you can get blown up very quickly. Blow up a few before you drive one. You can practice flying helicopters in empty servers. You do not want to crash a helicopter full of teammates.
• Don't snipe. It takes a good sniper to be a benefit to the team. The problem is everyone wants to snipe and too many snipers on a team probably accounts for 20% of losses. In my opinion, sniping is most useful to your team at medium ranges since you can use your motion mines.
• This might be a given to some, but don't camp, especially when you're attacking. Camping is staying in the same spot for more than a few minutes. The longer you stay in one spot, the more likely the enemy is going to find you and throw a grenade your way or otherwise kill you. Be a moving target both in firefights and in the long term.
• Spawn on your squadmates. You can spawn directly behind them by selecting them in the spawn menu. If the server allows you to see your squadmate before spawning then make sure he's not in too hot of a situation before you die alongside him and waste a ticket.
• Shoot in short bursts. Each shot adds to the spread cone of your bullets. Just pretend it's a pistol and click a lot.
• BC2 uses bullet simulation instead of traces. So at long distances you'll need to aim high and lead (aim in front of) your target.
• Did I mention you should spot?

You need to equip this part of your class's vehicle specialization:

Alternate Weapon Package

A weapons package that upgrades the targeting systems of vehicles and helicopters. It extends the effective range and accuracy of mounted weapons. - Adds an alternate weapons to the vehicle. Such as the M1A1, will have a secondary machine gun that you can control along with your main gun.

Its a vehicle specialization and requires 10,000 vehicle experience points to unlock.

More details here.