An annual sealing goes a long way toward preventing stains and discoloration.
Glazed ceramic tile is a terrific flooring material, but the grout between the tiles is very absorbent and stains easily. The most effective way to prevent unsightly stains is to
protect the grout with a clear silicone sealer. And the quickest, easiest way to apply the sealer is with a 2-inch-wide foam-rubber brush ($1.50 at any hardware store).
Don a pair of chemical-resistant gloves, then pour some of the sealer into a clean can or jar. Dip the brush into the sealer and carefully draw it along the grout joints, making sure you don't miss any spots. Apply a liberal amount of sealer to each joint, but be sure to immediately wipe up any sealer that spills over onto the tile.
For maximum protection, reapply the sealer every six to 12 months.