pick a gun you want to get good with and stick with it for a while.
Rifleman, hardest class
MG class, its all about position and setting up.
Support, weapons kick ALOT, takes alot of practice to control.
Sniper, not that difficult to use, but if you pick this class, focus on taking out the other teams snipers/mgers and pick off people on the other team who are in a good position and hurting your teams ability to advance.
Assault, by far the easiest class to use, but avoid engaging the enemy from far.
Stick with teammates, if you are on a ff server use caution when shooting, NEVER try and shoot around a player, you will likely tk them and annoy fellow friendlies.
The melee attack of the Assault class is your friend
And always run away from grenades unless you saw who threw them and you know you have enough time to pick it up and throw it back again.
if ff is on don't be an ass...watch your fire and watch were you throw your nades.
capture points that require more than one player is always priority! get them as quickly as possible since they much easier to defend than capping especially if the oposing team has already gotten hold of them.
when trying to cap a double capture point do not enter the zone until you have a teammate nearby to cap it with you...entering the zone on your own will only alert the enemy to your presence. instead you should wait just outside the capture zone till a teammate is nearby then you both rush in and cap it, this will give the enemy less time to react.
if your team is dominating the map you should try and avoid capping the last capture point(the ones closest to enemy spawn) last, instead you should leave an area you have lockdowned(but not captured) for last and ready to cap, when the last cap(the one closest to enemy spawn) gets taken. this tactic is more usefull in certain maps than others e.g. donner, avalanche and flash(that actually just makes anzio the only current map were I wouldn't recommend it...though it stills works) for example in flash because the map is so linear it often pays off not capping the second last cap untill you have the last flag. if you cap the the second last flag the enemy will know that your coming(and from which direction) and make it much harder for you to get the last flag...rather you should sneak around the second last flag and try and get in and cap their last flag, make sure that there is someone standing by at the second last flag to cap it the moment you get the last flag.
if your camping keep swifting position slightly, or after a couple of rounds the enemy will be on to you! if your either sniper or machinegunner when swifting position(longer distances) you should try and stay with teammates of other classes(rifle, assault, support) since your very weak when on the move.
don't leave your snipers and mgs undefended in areas with multiple entry points! if your support or assault and see a lone mg or sniper you should hook up with them and cover their back...yeah yeah it's boring job because he will most likely rag up the most kills...but guess what the game isn't about your personal kills but about your team winning...your team won't be winning if your snipers and mgs(who usually is able to lockdown a 90 degrees area) keeps getting gunned down from behind. so make sure you cover alternative routes that lead behind your snipers and mgs. likewise if you see sniper or mg on the move, move with them!
RISK YOUR LIFE WHEN IT COUNTS! you respawn in this game so a single death won't matter much if you managed to defend a flag! if you see a cap point being taken over(especially double pointers/ last flag) get there and kill the enemy, don't sit around and wait for them to take over!
use the ingame voice chat or shouts to alert your teammates to enemy presence. "GRenade", "sniper", "MG", "enemy behind us" are usefull to remeber how to access quickly. learn to recognice the rifle sounds in the game and the direction they come from...this way you can alert your teammates without first entering enemy fire zone.
if in a prone position and a grenade lands close by it is often quicker to pick it up(use key) and throw it away, rather than trying to get out of prone position and then run.
when sniping from windows if posible try and place your self(depending on lvl) so that you can duck out of sight using the crouch key rather than strafe keys. this is more usefull since you can better keep your target and make pot shots in case you miss a shot...having the rifle scoped doesn't change the speed from wich you go from crouch to standing, but it does change your strafe speed.
when using the bazooka or panzerschreck your often better of moving in, deploy, shoot and get out rather than deploying the bazooka then get into position at a crawling speed, the bozooka is rather big and easy to spot if your slowly appaearing from aroudna corner the enemy is likely to see you before you see them. when using the bazooka you should also reposition often since the smoke trail will revail your hiding place. when shooting long distances take into account that the shell will drop slightly, so you should aim slightly above your target.
erh..I probably have more...but now I feel like playing