WASHINGTON – Some of the mistakes people make with their credit cards are obvious: Paying your bill late will lead to astronomical interest rates and a late fee, and you could have negative info on your credit report for seven years.

Other mistakes are less obvious — like charging anywhere near your limit.

“This is a big trap,” says Gerri Detweiler of credit.com, “especially for people who are trying to maximize their rewards” and put lots of expenses on one credit card.

Detweiler says creditors look closely at the percentage of available credit you’re using, and that you shouldn’t consistently spend more than 10 percent.

She also says that closing old credit card accounts sounds tempting, but unless they’re charging you fees or refusing to drop you, it’s a bad idea.

“Suddenly you have less credit available — it looks like you’re closer to your overall credit limit,” she says.

Detweiler adds that you shouldn’t be afraid to shop around with other credit card issuers and use what you learn from them to haggle with your own.

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