where to start
Tile floors can take a beating like no other flooring style, and they're waterproof on top of that, but they still need care and protection. Give your tiles another line of defense by placing doormats at entryways to reduce the spread of dirt and soil. You should also consider placing your furniture on protective pads, so they don't scrape the tiles.
Tile is nothing if not simple, and so is taking care of it. You should vacuum, sweep, and mop your floors on a weekly basis to keep it looking polished and clean, or more frequently if you need to.
You may also consider having it steam-cleaned every few years to keep it fresh and beautiful.
spills & stains
Sooner or later, everyone spills something on their nice, clean floors. Luckily, tile floors are remarkably resilient and waterproof, so cleaning up is easy. All you need to clean a spill off your tiles is a damp towel.
But the grout sealing your tiles is another story. Grout can be stained by spills, so you should take care to clean it with a cleaner labeled specifically for treating grout stains.