A business plan contains several main elements. First, it lays out the mission and the goal of the business. The plan will spell out whether your company is in business to serve a greater good or simply to fulfill an unmet need. Determine whether your business will serve other businesses or supply products to consumers. These are all important elements that should be included.
If you need to get going quickly to ride the wave of a fad before it fizzles, then fast, bare_bones planning may be all you've got time to execute. This works best when you've already got the infrastructure in place, perhaps from previous projects or an established business, and you can simply shift energy and resources to the new idea.