Or don't. Sure it's a personal preference I know but I just think they're horrible things, I don't want a massive bulky camera, I just want it 10% bigger with space for all the controls the pro bodies have. Adding a big chunk to the bottom of the camera to hold an extra battery I don't need doesn't appeal much to me.
Worse still if you've used a camera with an integrated grip (D3 etc), makes them seem even more clunky going back to the add on grips. Lens mount isn't central, etc etc
Sigh...
Rant over. I just really despise the things, variation of pointless unless you have giant hands in my opinion.