The idea behind a pizza stone is to distribute the heat evenly across the pizza base and secondly to extract the moisture, so that your pizza dough is crispy. Heat is important in the cooking process of a pizza: all breads need a high temperature to cook. A little cornflour rubbed on the pizza stone before it gets heated can prevent the finished pizza dough from sticking. Because it is porous it does absorb other things such as soap and oil, which means that they should never be washed with a detergent and only ever with cool water when the stone is cool.

pizza stone  

How to use a pizza stone

The pizza stone has to be preheated in the oven before you begin to cook. Always place the stone in the oven before heating the oven. The purpose of this is to allow the stone to absorb the heat evenly. Once the stone has reached the required temperature, remember that you are working with a fire-brick and it will be VERY hot so handle with great care! If you place your cold pizza stone (no matter how expensive it was) into a hot oven it will very probably not withstand the thermal shock and it will shatter. 
The best tool to get a pizza stone out of the oven is a pizza paddle which slides underneath the pizza and can bring the stone out easily. 
Part of the trick of using a pizza stone successfully is to season it properly. In this context seasoning a pizza stone means ensuring that when the oil seeps into it, it is cleaned so that it encourages a non-stick patina which can only be acquired over time. When you take it out of the oven, place it on a heat resistant surface. Let it cool down naturally. Never let your hot stone come into contact with cold water as it may crack.

Cleaning your pizza stone

Use a knife or a fork to take off the obvious pieces of pizza from your stone and then wipe without any soap or detergent. Any form of detergent or soap will seep into the stone and it will make an unwelcome addition to your next pizza (you'll only do it once!). When you want to store your pizza stone why not leave it in the oven, it helps to season it when it is new and sits happily on the shelf until you next need it.