If your lender refuses, or is slow to act on your PMI cancellation request, write polite but firm letters requesting action. Such letters are important not only to prod the lender into motion, but to serve as evidence if you're later forced to take the lender to court.

After writing letters for a few months, court action may become your best option. Because the amount of money at stake usually isn't huge, small claims court can be a good avenue, and you won't need a lawyer to accompany you. For more information on small claims court procedures, including how to write polite but forceful demand letters, see Everybody's Guide to Small Claims Court, by Ralph Warner (Nolo).