Most future homeowners aren't able to cut a check for the purchase price, which means one thing: getting a mortgage. When you apply, the rate you receive – or whether you qualify for a mortgage at all – is heavily influenced by your credit score.

Three separate credit bureaus keep a snapshot of your financial picture. Equifax, Experian and Transunion assign you a three-digit number to represent how risky it is to lend to you; most scores are between 600 and 750, with 700 and higher generally considered good.

Here's how your score is calculated:

• 35% – your ability to make payments.
• 30% – the amount of credit available to you.
• 15% – how long you've had credit with each issuer.
• 10% – the mix of credit (short-term, long-term) you have.
• 10% – recent activity (new accounts, closed accounts).

If you're considering buying a home, start by checking your score. You're entitled to one free report each year from the bureaus through annualcreditreport.com*. If your number is lower than expected, review your report carefully for any errors and contact the appropriate company to correct them.

Maintaining and improving your credit score

Your mortgage rate won't be locked in until you have a purchase agreement finished, so here are some tips to keep your credit score trending up instead of down:

• Make timely payments. Creditors want to be paid, and they want to be paid on time. Make sure you're dealing with all your bills by the due date; a small missed or late payment will hurt just as badly as a big one. Any black marks on your record will matter less as time passes and you continue to demonstrate your reliability, however.
• Pay off old debt. Start with anything delinquent or past due, then focus on short-term debt with a high interest rate. (Lenders don't like to see maxed-out credit cards, for instance.) Reducing your current debt also increases the amount of credit available to you, which is a win-win for your score.
• But don't close any accounts. You may have forgotten about that department store credit card you opened and used once a decade ago, but don't cancel it now. That will ding you twice: more recent activity and less credit available.
• Don't open new accounts, either. Lenders want stability, and taking out new credit rocks the boat and affects your debt-to-income ratio. You'll also take a hit from the credit inquiry during the application process.