One of the major factors in your credit score: how much revolving credit you have versus how much you're actually using. The smaller that percentage is, the better it is for your credit rating.

The optimum: 10 percent or lower, says Barry Paperno, consumer affairs manager with myFICO.com.

One of the best ways of boosting that score is "paying down your balances," says Lauren Bowne, staff attorney with Consumers Union.

"Having the ability to use a lot of credit is good, but you have to have low balances," she says.

What you might not know: Even if you pay balances in full every month, you could still have a higher utilization ratio than you'd expect. That's because some issuers use the balance on your statement as the one reported to the bureau. Even if you're paying balances in full every month, your credit score could still reflect your monthly charges.

One strategy: See if the credit card issuer will accept multiple payments throughout the month.