The most obvious way to blow your credit score is to make a late payment. Even if your credit score is solid, a single missed payment could cost you as much as 100 points, say many financial advisers. According to the Fair Isaac, the company that calculates your FICO score, payment history accounts for 35 percent of your total score. And that credit score will help determine what kind of rates you can score when applying for home or car loans. So first things first: Figure out your credit score.

Your FICO score, a number between 300 and 850, is based on five criteria: payment history, amounts owed, length of credit history, new credit, and types of credit used. You can find out yours at myfico.com. According to Experian National Score Index, one of the major credit bureau companies, the average credit score in America is currently 692. Those with scores well above 700 will qualify for the best interest rates out there.

But even if you pay your bills on time religiously, your credit score may be endangered. Here are five charge card sins that could cost you some precious credit score points.