Your payment history has the single largest impact on your credit score -- 35% of it. Worse yet, dealing with your payment history may seem counter-intuitive.

For instance, you may have an outstanding judgement that is several years old -- it was never paid off, but there has been no activity on the account for years. In preparation for getting a mortgage, you decide to pay off the judgement and oops! You just made your credit score worse, because now that judgement shows as a current account, not an old one.

The best thing to do is to meet with a lender before attempting to clean up your credit. Trying to do the right thing may just end up being the wrong thing when it comes to fixing your credit.

Why does your credit score matter? It is the major factor in determining your interest rate and fees. It even may determine your minimum downpayment -- both translating directly into cash needed at closing and cash spent each time you pay your mortgage.

The take-away? If you're within 3 months of getting a mortgage, don't apply for, pay off, or close any loans or credit cards without speaking to a mortgage professional first.

(C) Susan Pruden.