There is little coordination in public games but a single player can be useful anyway.
I'm new to this, only level 9, but want to do my part to help my team win a CTF game.
Judging from my experience with BF3 and BFBC2 I would say the most useful way is to learn at least a little bit of every kit, watch the match development, check the number of kits chosen and switch kits as needed (cap, repair, harass the defense or distract by sabotaging their base).
Yesterday I tried switching between a raider to slow down the offense and later an infiltrator to distract defense (and cap a flag or two).
What would you suggest?