SmartMoney's "10 Things Your ... Won't Tell You" is the best thing I like of the magazine. This installment for credit card is of top-notch quality too. Take a look.

4. "Our 'freebie' rewards are anything but."

In the hypercompetitive credit card marketplace, rewards are a way for banks to target big-spending niche audiences — frequent fliers, for instance. But these programs often come with hidden catches, such as exorbitant interest rates and high annual fees, so it's important to do your homework. "[A rewards card] doesn't make financial sense for just anyone," says Manning, of the Rochester Institute of Technology.

Before signing on, figure out how much you'll have to spend to earn the incentives from a given card. If the math works out to anything less than one penny earned per dollar spent (or a mile per dollar in the case of mileage cards), then you could do better.

Also, be sure to look for the rewards that best suit your needs. For example, if you want an abundance of options, from retail goods and services to charitable donations, American Express's Membership Rewards cards let you accumulate points at the rate of a penny per dollar spent, double that at gas stations and drugstores. Or if it's air miles you're after, the United Mileage Plus Signature Visa is one card that stands out from the pack, with its 1-mile-per-dollar ratio and host of travel benefits, including upgrades.