Burned doll? Just so you know, I've burnt lots of dolls. Some got very dark brown, some just got a little darker and one turned greenish! I have learned from various tutorials and books to use series baking and watch the oven like a hawk. Timing varies depending on the thickness of the clay.
The most important thing you can do is pay attention to the recommended temperature for the type of clay you are using because different clay manufacturers (and clay types) state different bake temps and length of time to bake per 1/4 inch thickness!
Here is how series baking works:
Some say put your work in a cold oven, turn on to 230 degrees. When the oven temperature reaches 230, bake for approximately 9 to 18 minutes (time depends on thickness of clay). You must do a final bake at the recommended temperature to cure the clay when doing the partial bake technique. Some say put your work into a preheated oven and completely cure each time you bake. Every time you bake, when finished turn the oven off, open door slightly and then let piece cool completely before moving it.
At his stage you can smooth and correct the piece (see comments under "can you sand clay" post). Just remember that the piece is fragile if you did a partial bake. You can clean white scratches that you made while sanding the clay by using acetone but once you use acetone you are done. Acetone melts the surface of the clay. Use a tiny amount on a very small spot and be careful - you can ruin your work.
Sometimes, tiny parts (such as fingers) burn before larger parts are completely baked. Cover or wrap them with a thin layer of Polyfill before placing the doll, or doll parts, in the oven.
You will find the technique that works best for you. Experiment. And have fun; it's only clay!