Being better at FPS

[GreenBanana]

Hello!
In anticipation of PlanetSide 2, I began trying to be better at FPS.
Currently i'm playing Battlefield P4F because the close quarters maps really improve my reaction speed and the bigger maps allow for better vehicle awareness, both of which are skills that are needed if I wish to succeed in PlanetSide 2.

My question is: what do you do to be better at FPS? Can you suggest any games/videos/guides?

Notice:If you are suggesting games, don't suggest Tribes:Ascend or Blacklight Retribution because everyone knows about them, plus the visor and the skiing mechanic makes these games far too different from traditional FPS.