If you have worked in the industry for a while you have a great advantage over less experienced competitors. If you do not have experience in the industry, consider working for someone else for a while. Or find a similar business in another location. Go to any SBDC Business Information Center and ask for the Encyclopedia of Associations, which is published by Gale Research. Contact any applicable associations and ask what information they can provide.
Trade shows are also a valuable source.
There will be people from all manner of related professions. These can be a good chance to ask questions and make contacts. Don't forget your local library or bookstore. They have a variety of books on how to start businesses and write business plans. In addition, the Internet is loaded with business planning information, visit our links page.