I have some American Racing rims that I want to paint black. Any reccomendations on suface preperation and what type of paint would work best for a do it yourselfer?

I'd say primer and paint...

Or powdercoat (if it will stick/wont warp the wheel... dont know)

Thats just my thoughts..

Lawrence has a great write-up on when he did his. Check his website.
I recommend a good cleaning, scuff, self-etching primer, and a couple of coats of Wurth satin black. Clearcoat if you want over the paint.