Make an extra house payment each year.
If you make one extra house payment each year you will cut 5 years off of your total mortgage debt due. (A 30 year mortgage will be come a 25 year mortgage.) If you are unable to make this as a full separate payment I recommend dividing that payment up by 12 and adding to each of your monthly payments. (Make sure to note this money is to be applied toward your principal payment.)
Can’t make a full payment add an extra $100 toward your principal it will make a difference in the end.