Writing A Business Plan
Entire books are written about writing a business plan. The SBA says writing a business plan is one of the best things you can do to enhance the chances of succeeding in small business.
Yet, it is not so much the writing of the plan itself that matters, unless you are seeking external financing. It is the research of the industry and your idea that matters. Writing a business plan forces you to get specific. Any idea is a great opportunity, if it can be kept vague!
Writing the plan forces you to realistically confront important issues your business must face. Further, if you seek angel or venture capital financing, a business plan will be needed to present to them.
Key areas of a business plan must answer 1) How you will market your product? 2) What are the production costs of your product or service? 3) What is the background of the key members of your management team (for financing)? and 4) What is your long-term strategy and how does it relate to the strategy of your market competition.
For more information about business plans:
Planning Your Business (from CCH)
Business-plan.com (Anatomy of a Business Plan)