Echoing what the others have said, squad up. Either play with friends and form your own squad and use some form of VOIP (my friends and I play and we use our own Ventrilo since we all have it on voice-activated and talk the whole time. Not just about the game so we use our own but all have the in-game VOIP enabled for communicating to other squad members) to coordinate assaults and defenses and who's going to respawn as anti-tank to take out the APC that has the squad pinned down, etc. If you can't start up your own squad and have it be sizeable, join a squad with a couple of guys in it and stick with the squad leader. Follow his orders and request orders if he's not giving them. If I'm in a squad and the SL isn't giving orders or the other members aren't following them, I don't stay in that squad long.
That's the main thing: teamwork. The squad system exists for a reason and if utilized, it can be really effective. The whole safety in numbers thing, as well. It's way more fun to get in a great squad and go on a rampage than it is to lone wolf it the whole time.
My primary squadmate is going to be MIA a lot starting today but I'm still down for playing. If you ever want to play, just shoot me a PM here.