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.
Both new homebuyers and refinancers can get free access to the credit reports that lenders use by visiting AnnualCreditReport.com, a website created via Congressional mandate. A free report from each of the three consumer reporting agencies -- TransUnion, Experian and Equifax -- is available at no cost every 12 months. Check for errors; if mistakes are found, don't hesitate to dispute any and all inaccurate and derogatory items.
When refinancing, don't take the first offer that comes around. Instead you should actively compare both interest rates and lenders.
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.