When evaluating interest rates for a credit card, one of the key things to consider is the length of the introductory APR. Many credit cards offer a 0% APR for balance transfers or purchases during a promotional period, but once this period ends, the regular APR will apply, which could be significantly higher. Another factor to consider is the ongoing APR that will apply after the promotional period. Cards with a higher APR can lead to more expensive interest charges if you carry a balance.

In addition to the length of the promotional APR, it's also important to understand whether the APR is fixed or variable. A variable APR can fluctuate based on the prime rate, meaning your interest rate could increase even if you haven't missed a payment. Another factor to keep in mind is how the APR differs for purchases, cash advances, and balance transfers. Some cards offer a low APR for purchases but a much higher rate for cash advances. Understanding these distinctions can help you avoid unexpected interest charges.