1. Review your reports. Check your business and personal credit reports at least once a year to make sure there aren't any errors, says Raymond Joabar, senior vice president for American Express OPEN. Mistakes can lower your credit score and raise your interest rate. You can get a free report at AnnualCreditReport.com.

2. Don't apply for too many cards. Too many credit requests can lower your credit score, says Joabar. Make sure you have only as many cards as you need.

3. Ask for forgiveness. If you have made some late payments that are dragging down your credit score, call the company you paid late and ask nicely if it will take those late payments off your credit report. "The quicker you call, the higher the probability that they'll grant that request," says Brad Stroh of Bills.com.

4. Ask for a lower rate. If the customer service rep says no, threaten to cancel the card and sign up for one with a lower rate.