Look at your amortization schedule. If you didn't get one at closing, ask your bank for one, or make one yourself, with the current mortgage balance, interest rate, etc. Lots of programs floating around that you can use. Then, each month, pay your regular principal and interest (escrow?) payment, plus the principal payment(s) on the next few payments -- as many as you can afford. The next month pay the P&I on the next payment (Skip the ones you paid principal only on the month before) plus some more principal payments. This sounds complicated, but it's the same as adding $50-100 extra per payment, and you always know where you stand using the amortization schedule. We did this and paid off a 20 year loan in 9 1/2 years! It was easy at first, but got harder as the principal portions got bigger, which they do every month. Good luck!
Having no mortgage is a wonderful feeling.