If you have the money in your checking account to cover a debit charge, then you have the money at the end of the month to pay off in full any balance you have on a credit or charge card. If you don't carry a balance you don't pay interest.

I'm presuming you don't pay an annual fee (a lot of free Visa and Master cards out there). And as a bonus you can get percentages back. See here for more info:

http://www.fatwallet.com/forums/finance/632935