I teach that you should seek to learn from competitors; obviously never copy another business's idea or what they are doing, but you can absolutely learn from their mistakes or see what they are doing and discover ways to improve it. All of that analysis belongs in your business plan: make sure you have your competitors under the microscope and make sure that is a solid chunk of your plan. That is some of the best research and information you will gather about what will make your business successful in future.
The "Back of a Napkin" Plan: It is the source of entrepreneurial legend and lore, the million_dollar idea that was hurriedly scribbled on a bar napkin. Yet, for most potential business owners this option for business planning remains a fantasy. However, like any myth there is a tiny grain of truth inside. A quickie business outline can work as a launch plan under the right circumstances.