Paying a point for a six-month commitment on a fixed rate mortgage is reasonable, especially with a float option 60 days prior to closing. The float option will offer some protection in a downward interest rate environment, but don't expect to match the national averages for 30-year fixed if you float to a new rate 60 days prior to closing. The point paid for the loan adds about one-tenth of a percentage point to the APR of your mortgage.

New construction has the added risk that the rate lock expires before closing because of delays in construction. Make sure that the rate lock will extend past your anticipated closing date just in case the house isn't completed on time.

Bankrate has a weekly feature that surveys more than 100 mortgage professionals asking them whether it's a good idea to lock in a mortgage rate. Check out the Rate Trend Index to see what the experts have to say about whether or not it makes sense to lock in a mortgage rate. Whatever you decide, you can't be sure of getting the lowest mortgage rates between now and closing. If rates go down you'll wish you hadn't locked, and if rates go up you'll be glad that you did.