The average mortgage interest rate on a 30-year fixed-rate mortgage loan last week was still below 5 percent. Historically, that's an amazing rate.

That doesn't mean, though, that there aren't a whole lot of borrowers — or soon to be borrowers — who don't want to lower their own mortgage interest rates.

Unfortunately, the time to lower your mortgage interest rate is before you take out a mortgage loan. Yes, you can always lower your rate through a refinance. But that's a lot of work and paperwork. It's not free, either.

That's why it's so important to take the steps in your financial life to guarantee that you'll qualify for the best mortgage interest rate.

The lower the interest rate, the lower your monthly mortgage payment will be. And depending on the price you paid for your home, the difference between paying a 7 percent interest rate on your mortgage and a 6 percent rate could be significant.

On a modestly priced home with a 30-year, fixed-rate mortgage loan of $180,000, an interest rate of 7 percent will result in a monthly mortgage payment of $1,197.54. The same loan with an interest rate of 6 percent equals a monthly payment of $1,079.19. That's a difference of slightly more than $118 every month.

Lenders consider several factors when determining your mortgage interest rate. First, is the amount of money you can provide for a down payment. The standard down payment used to be 20 percent of a home's purchase price. During the housing boom of 2001 through 2006, lenders offered a host of low-down-payment and no-down-payment loans. Those have largely disappeared now that the nation is suffering a housing slump. The higher the down payment you put down, the lower your mortgage interest rate will be.

The length of your mortgage loan is also important. If you can afford the higher monthly payments, your interest rate will be significantly lower if you take out a 15-year fixed-rate loan instead of a 30-year fixed-rate loan.

Your own financial habits play a significant role, too. If you have a history of paying your bills on time - and the good credit report to prove it - and a high income and low amount of debt, you'll qualify for a lower interest rate. That's because lenders will view you as less of a risk for defaulting on your payments.