Find the NAICS (North American Industry Classification System) and SIC (Standard Industrial Classification) codes that apply to your industry.
Research your competition in the place where you plan to start your business. Search for industry information in a local newspaper.
Industry professional organizations collect data and statistics that may help with your business plan.
Find organization websites:
In your favorite search engine search the name of your industry plus the word "association" OR
Search Encyclopedia of Associations by the name of your industry