Start with your current lender. If you're a good customer-you hold a sizable mortgage, pay on time, and maintain good credit-your existing lender will probably do everything in its power to keep your business. The company may cut you a break on fees for things like appraisals, surveys, and inspections if the information is current and you meet other requirements.
Carefully review the estimated closing costs. If you decide to lock in the rate, the lender will send you a "good faith estimate" of your closing costs within three days. Go over the numbers carefully, and compare them to the ones that appear on the final settlement statement (the HUD-1) from your previous mortgage.
When it comes to lowering your rates you will need to weight the benefits of having a lower rate vs. paying points up front. You may end up paying a lot more depending on your choice and how long you plan on keeping your mortgage.
Don't rely on published rates. "No one's going to advertise their worst product," says Keith T. Gumbinger of HSH Associates, a Butler, NJ, firm that tracks mortgage rates. "They advertise the best possible rate, which probably gets offered to only the top 10 percent of applicants."