Best bet to properly manage your credit card is to buy things on it, but not fully pay off the entire balance. You want a history of steady, regular, on-time payments. For a total bump in credit rating your best bet is to have more than one card, and get a small personal loan from a bank, say $1,000, and pay that off steadily as well, so you have multiple streams of different types of credit established.
and... i like them? I think I like them.