Wood floors can have several different finishes. They can be installed first, then finished, or prefinished at the factory before installation. Polyurethane (pol-ee-YUR-uh-thane), either solvent- or water-based, is the most common finish, although penetrating oils and waxes are also used. Polyurethane floors will generally have a plastic look and be absolutely smooth. Run your hand across the floor. If you can feel the grain, you probably have an oil or wax finish. The first step in keeping hardwood floors looking good is to keep them clean. Just as sandpaper grinds away at wood, bits of dirt can abrade your floors every time you walk across them. Daily cleaning with a broom or dust mop should be part of your maintenance program. When moving furniture across wood floors, always lift, rather than drag. Wipe up any spills as soon as they occur. If your floor is properly sealed, you can damp mop it once a week to remove dirt. Use a cleaner specially designed for use on wood floors and immediately mop up any excess. To test if the finish on your floor has become worn, put a little water on a high-use area. If the water soaks in immediately, your finish has probably worn off. Short of stripping and completely refinishing the floor, you can apply wax to bring back the floor's original luster. Paste wax applied and buffed with a professional machine is ideal, but other waxes designed for use on wood floors are acceptable. The only thing to remember about waxes is that you have to strip them completely if you ever decide to refinish your floor. Often this is a process best left to flooring professionals.