With those holiday credit card bills now hitting mailboxes across the country, many people will be turning to special zero- or low-percentage teaser rates being offered by some companies.

The offers often sound like great ideas. Why not pay 15 percentage points or 20 percentage points less than what you’re forking over now?

But watch out.

“For instance, some people don’t understand that the zero percent rate is just an introductory rate,” says Jody Farmer, vice president of strategic marketing for CreditCards.com.

“The average duration of the offer is six months and then the rate will go to the standard credit card rate, which is about 17 percent,” he noted.

Also, those using a zero percent transfer should never put new charges on the card, he adds. That’s because the zero percent will be paid off first. New charges generally have a standard credit card rate.