You have to treat a credit card like a debit card. Pay it off before any interest accrues. I have a small card I got for traveling that I use for small internet purchases, it's got a $5k limit now (which kind of defeats the purpose I got it for), because I used it once in a while and pay it off as soon as the charge hits the account. They just keep upping the limit without me asking, I guess they're trying to lure me into using more.

Most morons (most people you know) think $5k credit line = I have $5k. You don't. You can borrow that much - and they'll take as much interest as they can legally can while you pay it off. Which is why I send my payment in as soon as it posts, because they got enough late charges on me due to "the system is slow and your payment didn't post in time" bullshit. The last one, i call and raised hell out of sheer principle and they removed it. I had their receipt email stating my payment had posted.

I hate and loathe credit card companies, but they have their uses, as long as you have discipline with them.