Just pay more
If you want to see magic, start playing with mortgage calculators and see how adding a little payment to your principal here and there can shorten the length of your loan. You can use Bankrate.com's mortgage loan payoff calculator to see how $100 or any other amount added to your payment reduces your interest and shortens the length of your loan.
If you pay a little more principal, you get a bonus. The lower your principal gets, the more every payment from then on is applied to principal, as less goes to cover interest expense.
If nothing else, round your payments up, recommends Tracy Piercy, CFP and CEO of MoneyMinding.com. She says that when people have a payment for $644, they think of it as $650. Why not just pay $650, then? An extra $6 a month on a $200,000, 30-year loan can save you four payments at the end of the mortgage loan.
When you pay extra, make sure the extra is applied to the principal balance, not just set aside for the next payment. And before you make extra payments, read your contract and make sure you won't have to pay prepayment penalties.