Your monthly mortgage payment depends on your credit score, the size of your down payment, and whether you pay discount points. A down payment of less than 20 percent forces you to buy mortgage insurance, get a piggyback loan, or pay a higher rate.

The credit score is a reflection of your credit history -- whether you pay bills on time, how much debt you have, how much you earn, the types of debt you have. Before applying for a mortgage, get copies of your credit reports so you can have time to correct any errors. You can find the credit bureaus' contact information here.

Often, a down payment of less than 20 percent means that you will pay a higher interest rate, and that you will have to buy mortgage insurance or get a piggyback loan. People with little or no down payment money can get mortgages, either through FHA and VA programs, or getting contributions from down payment assistance programs, or getting zero-down loans at higher interest rates.

You can reduce your mortgage rate by paying discount points. A point is 1 percent of the loan amount. Paying discount points makes sense only if you have the mortgage long enough for the lower monthly payments to make up for the out-of-pocket expense of paying the points. This "payback" period usually takes a few years.

The rate that you pay depends very much on what is happening in the secondary market where your lender gets its money.