By not paying your bills as agreed. Keep in mind that bad entries are reported to the credit bureau if you are over 30 days late from making a payment but make sure that you payment get posted prior to 30 days. Example if you have a car note and its due on the 9th of each month, it will not get reported to the credit bureau unless a payment is not posted by the 8th of that next month as long it will not go over 30 days. You will have to pay late fees but it won't affect your credit. Source: Credit Bible by Phil Turner.