Scrape the pizza stone using a kitchen scraper to remove any burned on pieces of toppings or crust.Wipe the stone with a clean damp sponge or towel.Submerge the pizza stone into a sink full of clear, plain, warm water.Soak the stone for 20 minutes to completely saturate the porous ceramic surface.Dry the pizza stone on a drying rack overnight.Repeat the last three steps up to six times and then bake some pizza dough on the stone. If the stone still has a soapy smell, replace it.
and remember:
It is normal for pizza stones to discolor with use. Discoloration and stains will not hurt the stone or change the taste of the pizza.
Rub a mixture of baking soda and water on the stone with a toothbrush to remove small stains.
Never put soap on a pizza stone or soak it in soapy water. Most pizza stones are made of ceramic that is porous and soap will absorb into the stone. The soap will then be released from the stone when you cook with it.
Never put a hot pizza stone on a cold surface, as it may crack.
Excessive oil buildup on a pizza stone may cause it to smoke when it is being used.