What is the best way to clean hardwood floors?

Most hardwood damage is abrasion, not dirt: fine grit tracked in from outside acts like sandpaper underfoot and dulls the finish. So the highest-value habit is frequent dry cleaning, a vacuum with the beater bar off or a microfiber dust mop, plus doormats at every entry. For the actual wash, use a barely damp microfiber mop and a cleaner formulated for finished wood, wringing until it is nearly dry, since the floor should look dry within seconds rather than staying wet.

What to avoid is more important than what to buy. Standing water seeps into seams, swells the wood, and lifts the finish, so no sloshing buckets. Steam mops force hot moisture into joints and are explicitly discouraged by most flooring manufacturers, and they can void warranties. Skip vinegar and ammonia solutions, which can etch polyurethane over time, and skip oil soaps and wax-based products on modern polyurethane floors, since they leave a film that complicates future recoating. Felt pads under furniture, trimmed pet nails, and keeping indoor humidity roughly between 35 and 55 percent to limit seasonal gapping do more for a floor's life than any cleaner.