Before you refinance a loan, make sure that you carefully analyze any fees that your lender is including on the loan. The Department of Housing and Urban Development can provide you with a list of standard fees. Use it to make sure that your lender isn't tacking on anything extravagant. And by all means, compare their fees with other lenders in the market.
If you know that you will be moving in 3 to 5 years, you might want to consider refinancing to a 3 or 5 year ARM (adjustable rate mortgage). These loans typically have a much lower rate that a traditional fixed rate loan such as a 30 year fixed, but they do have a fixed rate for the first 3 or 5 years of the loan. This will enable you to benefit from the lower rate, but you won't ever have to worry about the risk of a rate adjustment because you will be selling the home before the fixed-rate period ends.
Get your interest rate and closing costs in writing as soon as you decide on a lender to work with. Get your lender to give you a commitment in advance of all of the costs that will be involved with your loan. Find out if the refinance loan you are getting has a pre-payment penalty as well. Sometimes lenders will leave out important information like this, if they think it might scare you away from refinancing with them.
Stick with a simple loan. It is easier to understand and less likely to get you into trouble. Adjustable-rate mortgages may seem like a way to get a bigger house now or to keep more money now, but when the rates adjust you can get into trouble. Avoid anything with a balloon payment. Just choose a simple 30-year mortgage you can easily afford.