I map everything i can to something i can reach with my wasd fingers, so basically

1234

qwert

asdf

zxc



with the red letters being the ones i bind for movement or other purposes, all the others i try to bind, then bind the shift and alt varieties if i'm running out of room. i play almost exclusively toons that can heal and damage (priest, pally, now shaman) so if my focus is dps, then damage spells get the vanilla binds, healing gets pushed to shift binds. my right hand pretty much stays glued to my mouse, so aside from mapping mouse clicks to buttons (which i plan on doing) those are the buttons i use. Buffs, eating, non-essential totems i plan on binding to the right side of my keyboard since they are lower priority.