Interest rates on credit cards may be fixed or variable. Whichever you choose depends on whether rates are headed up or down.

If a rate is fixed, Truth in Lending laws require that a lender provide at least 15 days notice before raising the rate. However, some states may require more notice.

A low-rate card with a fixed-rate may be an attractive option---particularly if your issuer has promised to keep that rate fixed "for life." However, the bottom line is that if your issuer is required to provide just 15 days notice before a rate change, the fixed-rate card is not all that much different from a variable-rate card. So it pays to look closely at the rate and fees of both.

With a variable rate, the rate may be subject to change either according to a formula determined by your credit card issuer, or totally at your card issuer's discretion. The rate may be subject to change monthly or quarterly, too. If rates are on their way down, you may want to consider a variable rate card.Tip: If you do choose a variable rate card, check to see if there are any limits as to how high or low the rate can go. Why? Because if the lowest variable rate possible on your card, for example, is 14.9%, and rates are trending downward, you may want to switch your card to another issuer.