Pop quiz: Which affects your credit score more, getting married or having overdue library books?
Surprise answer: A library fine that goes to collection can shave 100 points off your credit score -- and boost your annual interest payments by hundreds of dollars. But getting married doesn't affect your score at all unless you co- sign for a loan with your new spouse.
Your credit score -- the numerical summary of how much you owe and how promptly you pay your bills -- has a major impact on your finances and beyond. Score high and you can save thousands of dollars on your mortgage, car loan and credit cards.
A good score can also reduce your premiums for auto, homeowners and private mortgage insurance. Auto insurers use credit scores to assess your risk of getting into an accident because studies show that consumers with high scores tend to file fewer claims. [More: 5 ways to boost your credit score]