How much do you spend a month, and what is it usually on? Try to think of all the things that you normally spend money on, and which of those could be paid for with a credit card. Stuff like rent, certain bills, mortgage, etc won't work with credit cards. But most everything else will.

When you say your credit is good, but not great what do you mean? Is it because you just don't have credit history, have late payments, foreclosure, etc?