In certain cases, you might not have to do anything. If you locked in a solid mortgage rate during a previous period of low interest, keep making your payments. As real estate values normalize over time, you'll eventually regain home equity.
However, if your credit score is better now than it was when you originated your home loan, you may want to lock in today's best mortgage rates. Or you may qualify for a government-backed plan that can help your mortgage lender process a refinance. FHA, Freddie Mac, and Fannie Mae all have special money-saving programs. If your mortgage is backed or held by these entities and you meet some other qualifying criteria, you can cut the amount of interest you'll pay over the life of your loan.