If you're thinking about buying a house or a car, your credit score is a very important number.

The interest rate you'll pay for the money you borrow will be determined, in large part, by this three-digit number that's generated from the information in your credit report.

Most lenders have carved-in-stone rules about handing out the best terms, and those rules almost always place a major emphasis on your credit score. If their best rates are offered to borrowers with a score of 700 or higher and yours is a 698, those two points could cost you thousands of dollars.

According to www.myfico.com, the consumer Web site of the Fair Isaac Corp. that created the FICO score (the most commonly used credit score), the interest rate difference between those two scores is about one-third of a percentage point.

On a $165,000 30-year fixed rate mortgage, that third of a point could cost you more than $11,172 in interest charges, assuming 629 percent is the lowest rate available (see Bankrate's calculators). Fall below a 660 and the rate goes up another .81 percent.

Keep in mind that these are averages. Most lenders today practice tiered pricing, with interest rates rising as scores go down. Each lender chooses its own "break points" between tiers. Lender A may bump up the interest rate if a score falls below 700, while Lender B doesn't charge higher rates until the score is 690 or below. So if you stick with one lender, and that lender's break point is 700, raising your score from 698 to 701 can be vital.

This underscores the importance of not only doing all you can to improve your score, but shopping thoroughly when looking for a mortgage. From the perspective of a mortgage broker, who can choose among a sea of many lenders, there are no sharp break points. Consumers should do what a good broker does -- look for a lender that offers the best rate for a specific score.

But that's jumping ahead of ourselves. First things first: You can take steps to improve your credit score. The number of variables that play into an individual score make it impossible to say that one particular action will increase a given score by a certain number of points. But there are some good guidelines.

"The mantra for getting a great score is pay your bills on time, keep account balances low, and take out new credit only when you need it," says Craig Watts, consumer affairs manager for Fair Isaac Corp.

"People who do that faithfully have very high scores. It usually means you're being conservative and cautious about credit. It's not a toy and it shouldn't be a hobby."

Speedy upgrade
That's good advice, to be sure, but these actions take a long time. What if you're house hunting and you just need a few extra points to bump you over the line to the great rates?

Start by pulling your credit report and your credit score to see where you are. To get an estimate of your credit score, check out our Credit Score Estimator. If your score is above a 760, you're golden. Improving your score from 760 to 800 won't get you better terms.

Good Luck.