If you do not plan on staying in the house very long, refinancing may not be in your best interests.
Resist "no cost" refinancing. No cost doesn't mean free. On the contrary: The closing costs are usually bundled into the new mortgage, which means you pay interest on them. The fees associated with a 30-year mortgage could cost you more than double what they would have had you simply written a check for them at closing. Or, if the costs aren't bundled in, you'll be charged a slightly higher interest rate. Either way, the lender wins.
There is a refinancing myth that says you should not refinance your mortgage unless your interest rate will be at least two points less. This myth is not necessarily true if there are other benefits to the refinance or other reasons behind it.
These days most people request a Good Faith Estimate (GFE), but have no clue what to look for on the GFE. Make sure you request a GFE that has ALL fees estimated and disclosed. This includes: origination points, processing, lender, appraisal, title, escrow... ALL FEES... especially the Yield Spread Premium or YSP.