Pull your credit report from the bureaus and review it for any negative items (late pays, collections etc) and inaccurate detail. Try to dispute negative items and remove them from the report. If required pay off any unpaid debt. Otherwise, you won't get a low rate and may not even qualify. Of course there are lenders in the subprime market who may offer you a bad credit refinance loan, but it's better to avoid them as they'll possible charge higher rates and fees.
Almost 30 million Americans qualify for a VA Loan. With a VA Loan, you can qualify for a VA Streamline Refinance. You may also be able to refinance your home with an FHA Streamline refinance.
The length of time that you expect to keep the mortgage helps you determine whether it is worthwhile to pay points up front to reduce your interest rate. Unlike points paid on your original mortgage, points paid to refinance may not be fully deductible on your income taxes in the year they are paid.
Refinancing may not be that useful if you have already used up 90% or more of your home value in taking out a mortgage or any home equity loan. You won't be able to get the best rates available in the market as when you refinance a 90% LTV loan, you will probably require a loan of that value or higher. This will be quite closer to being a 100% financing option and hence mortgage refinance rates will be comparatively higher. Moreover, 100% loans are hardly available in times of mortgage market crisis.