When ever possible, dance on sprung wood floors. Dancing on hard surfaces without give- concrete, marble, wood directly over concrete, etc. will injur your joints and muscles. If you happen to fall on these surfaces you will be much more seriously hurt then if you were to take the same fall of a sprung floor.
Never spin on carpet with fresh suede or rubber soled shoes. It is very likely you will injure your feet, ankles, and knees.