The first step involved in writing a business plan is the executive summary. Here, include everything that you would cover in a five minute interview. Explain the fundamentals of the proposed business: What will your product be? Who will your customers be? Who are the owners? What do you think the future holds for your business and your industry? Make it enthusiastic, professional, complete, and concise.
So how would you go about making a plan like this? Well if you know a fair amount about business, you can. It will take some special calculations and some work but if you know how to put together a Profit & Loss Statement, you can probably do it.