For the homebuyer that is "shopping" for a mortgage, or waiting for rates to fall, or just "hasn't gotten around to it", we suggest you almost always lock, and to do it quickly. The sooner you lock your rate, the less chance you have of losing in the Mortgage Rate game. If you are refinancing, you can gamble a bit more, but if you have a signed purchase contract in hand, lock your rate as soon as possible.  There is no better way to protect yourself from the fickle mortgage markets. Holding out for 1/8th - 1/4% more is just not worth the risk!