1) Taking only ammo once you've picked up that particular weapon already.
2) When an enemy takes the time to avoid typefragging me, I return the favor by not pursuing him once I've finished chatting. Often I will try not to frag him until after my next death.
3) When I get to an enemy base and a team member is already there waiting for the flag, I don't grab the flag and let him have it. After all, first come, first serve.
4) When an FC is in the base waiting for the retrieve, I don't take any HP/Armor powerups nearby.
5) When I see our FC coming back from the enemy base, I cover his back by doing my best to slow down the pursuers even if it means I die.

6) After a successful flag capture, I take the time to defend the base until another team member makes a flag cap.
7) I try to say sorry everytime I teamkill accidentally.