Annual percentage rate (APR). The APR is a measure of the cost of credit, expressed as a yearly interest rate. Check out the "periodic rate," too. That's the rate the issuer applies to your outstanding balance to figure the finance charge for each billing period. For example, if you have an outstanding balance of $2,000, with 18.5 percent interest and a low minimum monthly payment, it would take over 11 years to pay off the debt and cost you an additional $1,934 just for interest, which almost doubles the total cost of your original purchase.

Grace period. This is the time between the date of a purchase and the date interest starts being charged on that purchase. If your card has a standard grace period, you have an opportunity to avoid finance charges by paying your current balance in full. Some issuers allow a grace period for new purchases even if you do not pay your balance in full every month. If there is no grace period, the issuer imposes a finance charge from the date you use your card or from the date each transaction is posted to your account.

Annual fees. Many credit card issuers charge an annual fee for granting you credit, typically $15 to $55. Some issuers charge no annual fee.

Transaction fees and other charges. Some issuers charge a fee if you use the card to get a cash advance, if you fail to make a payment on time, or if you exceed your credit limit. Some may charge a flat fee every month whether you use the card or not.

Customer service. Many issuers have 24-hour, toll-free telephone numbers.

Other benefits. Issuers may offer additional benefits, some with a cost, such as: insurance, credit card protection, discounts, rebates, and special merchandise offers.