One of the major factors in your credit score is 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: 30 percent or lower.
To boost your score, "pay down your balances, and keep those balances low," says Pamela Banks, senior policy counsel for Consumers Union.
What you might not know: Even if you pay balances in full every month, you still could 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 will still consider your monthly balances.
One strategy: See if the credit card issuer will accept multiple payments throughout the month.