When reviewing any cards, read the fine print carefully. Promotions for the Discover More Card prominently boast of a "5% Cashback Bonus." Here's the gotcha: You get 5% back on spending categories that change every few months -- from January through March 2010, it was travel -- 0.25% on all other purchases up to $3,000 and 1% on purchases above that amount.

The Chase Freedom Card promises "3% Bonus Cash Back." What you really get with this product, besides interest rates that range from 13% to 23% depending on credit history, is 1% cash back on the vast majority of purchases and 3% for purchases "in popular categories that change, like gas, home improvement and department stores." You'll have to sign up for the Chase Freedom before receiving a full list of terms.

And here's the final rub with these cards: The ones with higher rebates for gas, groceries and the like sometimes fail to compensate you fully for such purchases. If you happen to patronize an independently owned gas station or grocery store, there's a chance your card company's purchase-coding system won't recognize it and you'll get the lower rebate rate.

"I've personally called up my card company before to complain about that," says Weber, of SmartBalanceTransfers.com. "Usually, I got stonewalled."

The smartest option of all: Get the cash-back card best tailored to your spending habits and religiously pay off your balance each month.

This article was reported by Asher Hawkins for Forbes.com.