Starting a sole proprietorship is easy, though different states will have different regulations regarding the process. Many times, all it takes is filing a DBA, or "Doing Business As" form with the county Register of Deeds. This will allow the sole proprietor to use a business name other than his own for business purposes. This is necessary if a sole proprietor wishes to do business in any name other than his own, and will help establish the entity separately of the person for accounting purposes.
Depending on the nature of the business and the location where it operates, other permits and forms may be necessary to file. Check with your local Small Business Administration to ensure you are in full compliance with all local, state, and federal guidelines.