In order to have clean ceramic tile grout you will need to keep up with it on a daily basis. If it is in a bathroom shower, wipe it down daily after it is used to keep mildew and mold down. If it is on kitchen counters, you will need to wipe it with a sponge and plain water daily to keep the food debris from staining your grout. For a weekly cleaning, mix a 1/2 cup of hydrogen peroxide with a 1/2 gallon of water and wipe down the surfaces. Your tile will need a new coat of sealer when the grout shows that it is holding debris and water spots, or if there are stains which are hard to remove.