Round your mortgage payment up to the nearest $50 or $100. The small extra amount goes directly to principal every month. Almost painless — meaningful results over the life of the loan.
Tight budgets where even $25–$50 extra per month is all that's available.
If your payment is $1,347 — pay $1,400. Label the $53 as principal only.
Set this as your fixed auto-pay amount going forward.
Revisit yearly and round up to the next $100 if your income has increased.