Just a note on builds - You will respec at 70.
The general rule is that you'll spec a certain way to help with questing/grinding (and a little PvP on the side) then reset your spec at 70 for what you want to specialize in (instances, raiding, Battlegrounds, Arena, etc).
The build shoarmakip suggested for 33 is a solid Siphon Life build for the level. Personally I'd move the points in Amp. Curse and CoEx to Empowered Corruption. In BGs (mainly AV right now) I find that I'm fear-doting and moving on rather than focus-firing a single target. But that's just my preference and your play style should be your ultimate guide.
Also, it's far easier to grind BGs at the "nines" (19, 29, 39, etc) except AV which is better to do on the "ohs" (50, 60, etc).
Happy hunting!