Mix one to two cups of oxygen or chlorine bleach with one gallon of warm water. Apply the mixture to the tiles liberally to soak the area, especially along the grout lines. After 30 minutes, add some more cleaning mixture to moisten the tiles and grout again and scrub them with a nylon bristle brush. This will effectively clean the tiles and get rid of mildew.
Spray pure, undiluted white vinegar on the tiles and grout to get rid of mildew and soap scum as an alternative to the bleach. After 30 minutes, scrub the tiles clean.
Mix equal parts of white vinegar and water together in a spray bottle to maintain your shower and keep it sparkling clean. Alternatively, mix one gallon of water with one cup ammonia, half a cup vinegar and a quarter cup of baking soda. Spray the tiles, let it sit for 10 to 15 minutes before wiping the tiles and grout with a rag or sponge.