Clean the surface of the tile with a degreaser cleaner designed to strip grease and wax off the surface of the tile. Use a rag and wash the floor with your hands instead of a mop, which can simply push dirt around. Get the floor or surface of the tile as clean as possible. Dry the tile thoroughly with a towel before moving on.
Place a piece of 220-grit sandpaper onto an orbital sander and sand the glaze off the surface of the tile. You do not have to sand all of the glaze off. You simply need to remove the glossy finish from the glaze. Removing just the gloss keeps the tiles sealed to prevent the tiles from soaking up moisture.
Wipe the surface of the tile off with rag wet with clean water, to remove all of the sanding residue. Do not use chemicals to clean the floor at this point.