If you're getting the card for points or rewards, this is one you definitely need to ask, says Josh Frank, senior researcher with the Center for Responsible Lending. Some issuers will revoke rewards if you're late with a payment by even one day, he says.

"A lot of times, the answer they will give you is that they can take away or reduce your rewards for any reason," he says. While that's true, the issuer will have a policy on revoking or reducing points, and that's what you want to ask about, he says. Under what specific circumstances would they reduce or eliminate a customer's points?

In most cases, "this is one the customer service agent should know the answer to," he says.