Someone asked Albert Einstein what he felt was his most important discovery. It is reported that he said it was the Rule of 72—Compound Interest Theory—which is used in almost all business transactions today. The Rule of 72 says that the number of years it will take to double an investment (or a debt) can be found by dividing 72 by the interest rate.
Compound interest means that those cool shoes you bought on credit for $100 could end up costing you double or more in added interest if you only pay the minimum payment.
To protect your credit—pull your credit report once a year, pay your bills before they are due and never, ever allow your mortgage to be late.