The idea behind a pizza stone is to distribute the heat evenly accross 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. The good news is that a pizza stone is a form of terra cotta and the cheapest ones work as effectively as the expansive ones.
In fact a home made pizza stone made from a terra cotta tile is perfect providing that it is unglazed. The theory is that because the pizza stone is made from natural clay it is porous it is capable of extracting the moisture from the pizza to ensure a crisp base. However its porous properties mean that basic care is necessary for the maintenance of a pizza stone. Make sure you don't use a glazed tile, they contain lead, what is very hazardous for your health.
The pizza can stick but a little cornmeal rubbed on the 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, only with cool water.
The pizza stone has to be preheated to a certain temperature to work and that often means leaving the oven on for quite a while before you begin to cook. Always place your stone in a cold oven and then turn the oven on. The purpose of this is to allow the stone to absorb the heat evenly. Once the stone has reached the required temperature then it is far too hot to handle with a conventional oven glove. Remember that you are working with a fire brick! 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 is a large wooden handle that looks like a paddle which slides underneath the pizza and can bring the stone out. The biggest drawback in familiarizing yourself with your stone and your oven will be how much cornmeal to dust on the stone before cooking. Too little and you will never get the pizza off the stone.
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. I use another cold tile and let it cool down naturally. Never let your hot stone come into contact with cold water, that can make it crack.
Pizza stones need preheating before you use them, which leave you in the unenviable position of trying to stretch the dough on a hot stone. Make sure that you have a paddle to place the stretched pizza directly on the stone.
Some pizza stones are so heavy you can hardly lift them and the sheer weight of them is an accident waiting to happen at some time.
When you use a pizza stone there as many reasons for having a soggy bottom as there are with regular conventional cooking methods. Here are some possible reasons for a soggy pizza base: