At this point, you may be tempted to skip writing a business plan altogether, viewing it as an unnecessary exercise in jumping-through-the-hoops, suggested by some old business professor who probably never held down a "real" job anyway.
There are a number of ways of going about the process of writing a good business plan. One of the most tried and time tested ways that works well is using a business plan template.
While these are easily available online, some of them are way better than the others. A lot depends on the approach that goes into writing the business plan.
Marketing - How is the product or service priced? How will it be distributed? How will it be promoted? Will it be promoted by the venture or an outside agency? What agency? How have you determined what amount to set aside for marketing? How have you determined product or service forecasts? Possible Data Sources: on-line searches; Amazon; local outlets; trade journals; industry attorneys & accountants; salespeople.