If you clean the tiles regularly with soap and water you can maintain them well and would not need other means to clean them. For buildups use white vinegar mixed in warm water and dry it off with an old towel. Works absolutely great.

You can get tile cleaning solutions from a supply store but make sure to ask for non-abrasive solutions as abrasive ones may destroy the luster of glazed tiles. Also pay attention to the spaces between the tiles as dirt accumulates between these areas. Clean this grout area with a brush, soap and water and if it is very dirty use a cleaning agent.