Credit card issuers offer rewards as incentives to get people to sign up for and use their cards. They’re a great way for them to target specific demographics, too. There are several cards that offer frequent flier miles, some have cash back rewards programs, some give free gas or other perks for using their cards. But be sure to read exactly how the rewards programs work so you can make the most of them, instead of letting them make the most of you.

If you don’t pay off your balance each month, you may not be able to really take advantage of the rewards. Gail Cunningham, a spokeswoman for the National Foundation for Credit Counseling said in a Smart Money article, “What people tend to do with rewards cards is charge everything,” she says. “But if you’re a person who carries a balance month to month don’t consider [such a card] because you’ll be paying interest on it and probably not gaining the rewards you should.”

Some of these cards lure you in with their attractive rewards packages, but make sure they don’t have high annual fees or interest rates that might make the rewards less rewarding. In the long run, it may end up being less expensive to just pay for the flights or filling up your tank. Credit.com has a list of rewards cards and with their interest rates so you can compare.

For travel rewards, be sure to look into any blackout dates when you can’t use your rewards to fly. If you’ve been trying to save up to travel during Christmas, but they won’t let you, you don’t want to have to spend extra money on additional travel some other time of year, just so you can use your miles. If they offer cash back, see if there’s a limit on the amount you can earn. No point using the card more than you need to, if there’s little benefit.

As with anything, if something seems too good to be true, it probably is. Knowledge is power!