Secured credit card. In the ask the loan officer thread,
NoSoup gave some advice (click for a link to the post) that would probably be more accurate than anything I could say.
Basically, you put 500$ in a (low interest, ik) account, and they issue you a credit card with a 500$ limit. You still have to pay off your credit card like a normal one, but they aren't taking much of a risk (they have your cash, bwahahaha).
Apparently, you also want to use it at least a small amount? Know even less about that part of the "earning credit" mojo.