Mineral deposits - Wipe with white vinegar or a solution of equal parts ammonia and water, rinse well, and pat dry. You can minimize water stains on tiled surfaces around showers, tubs, and sinks by wiping these areas dry after each use.
Mildew: Spray mildewed area with a commercial mildew remover or a chlorinated-bleach solution. Wipe with a solution of baking soda and water to remove the chlorine odor.
Stubborn stains. For stains that have penetrated deeply into the stone or bisque, use oxalic acid, which is a strong chemical bleach. Follow directions on the label carefully as this is a corrosive poison. After removing the stain, rinse tile well with water and let dry.
Oil: To remove oil from pavers, use a liquid mixture of plaster of paris to draw out the stain. Brush plaster over stain, leave for 24 hours, and brush off with a broom. Repeat as needed.
Paint. To remove paint from tile, apply a commercial paint remover, leave on for an hour, then carefully scrape off paint with a razor blade.
For general grout maintenance after a bathroom renovation, use a stiff brush, and scouring powder that does not contain bleach. Test the cleaner in a concealed area to make sure it doesn't discolor the grout. Always be on the lookout for chipped and cracked grout and repair flaws as soon as possible.