A cash-back rewards credit card is no good if you're letting free money slip through your fingers. And that's a common problem.
A study done in 2011 found that while the average household earns more than $620 in rewards every year, $205 of that goes unredeemed. So, if you have to register online to maximize your rewards, a step required by some cards, don't forget to do that.
Keep tabs on when points will expire and make rewards redemption an annual practice, so you won't lose out on anything you've earned. Make sure you've chosen a card that matches your spending habits and doesn't save the best rewards for stores and businesses that you don't tend to patronize.
Pay off your card balance every month, so that the cash back you're earning isn't being eaten up by interest payments. And always pay your credit card bill on time, because if you're delinquent, the issuer can take your cash-back rewards away.