There may be a variety of costs for using a credit card. The only way you can be sure what those costs could be is by reading the fine print of a credit card agreement.

It will include all the rules and regulations for the card and the possible penalties if you don’t live up to your side of the agreement. Here are some of the things to look for:

• when the interest rate can change
• whether there is an annual fee for using the card
• the fee you’ll be charged if you pay late
• whether you’ll be charged interest even if you always pay your bill in full and on time

New rules that went into effect in 2010 have added some protections for credit card users. Now you always have at least 21 days to pay your bill, starting with the day it is mailed.

But you’ll still want to approach any credit agreement with caution.