Most flooring installers spend little or no time working on the subfloor unless this was discussed beforehand and negotiated as part of the price of installation. If your subfloor is less than perfect—if there are dips or other flaws—you can do some prior work to secure the subfloor and fix any imperfections in it. Your goal should be a subfloor that is perfectly flat and smooth and firmly secured to the floor joists. If the installers arrive at a well-prepared subfloor, the new wood flooring will go in smooth, tight, and flawless.