(MONEY Magazine) – It's no secret that most major credit-card issuers woo customers with ultralow rates and then hike fees to make up for lost profits. But First USA, the country's second largest issuer, was recently stung by this strategy. In August, the company disclosed that its stiff late fees had prompted some cardholders to take their balances elsewhere. Although First USA blamed the problem largely on an outside processor (which they're no longer using) that was charging late fees based on when the check was processed, not when it arrived at the firm, investors reacted strongly; stock in First USA's parent, Bank One, has since fallen 35%.

First USA customers need not react as drastically as Wall Street, but they should be aware of First USA's hair-trigger late-payment policies. Until recently, if First USA received your check after the morning of the due date, you'd be charged $29. Others, including Capital One, are equally aggressive. "Issuers have essentially laid land mines around the terms of their cards," says Robert McKinley, president of CardWeb.com. "If you want a good rate, you have to play by their rules."

Since June, First USA has softened those rules. You now have until 10 a.m. the day after the due date before you're charged $29. And that fee is waived if your balance is below $50. Even considering this reprieve, with most issuers you need to mail your payment well before the due date. If you can't, most will let you pay on the website or by phone.

You can also take your business to a more "friendly" issuer. AmEx waits 15 days after the due date before charging a $25 late fee. A handful of others, Wachovia (800-842-3262) and USAA (800-922-9092) among them, have been slow to adopt cut-throat fee practices. "These banks have a long history of being pro-consumer," says McKinley.

--S.R.