The Small Business Administration in the US provide information which may help to answer your questions.  You'll probably want the section on "starting & managing a business" and perhaps more specifically "incorporating & registering a business".

There's also an eHow article on "how to register a business in America" which has some brief information and links, although obviously keep in mind the non-official nature of the information and be sure to verify the facts before relying on anything.

The Small Business Administration in the US provide information which may help to answer your questions.  You'll probably want the section on "starting & managing a business" and perhaps more specifically "incorporating & registering a business".