I have been putting together business plans for over 25 years and it is clear to me that the strength of its core rests solely on being able to execute the plan. Each year I approach business planning as an opportunity, rather than a burden. I would rather invest the time up front in mapping out the upcoming year, than leaving it to chance to dictate my strategy. While this may force me to think strategically as well as tactically, preparing a detailed business plan in advance enables me to identify the challenges in advance of actually facing them.
When you, and your partners if any, have all the core skills and industry knowledge you need to start right away without seeking experts, napkin notes may be enough to get going. Let's say you are already an expert in technology and social media. Then you, and your team, probably don't need a detailed plan to start developing a new app. You will draw on your knowledge and experience, and you understand that you might need to go back and do some more detailed and formal planning later. Certainly when you reach the point where you are looking for investors or lenders, you will move beyond those first casual notes. Until then, drawing upon your expertise can allow you to quickly jump into the market and perhaps gain a competitive edge by using a minimalist plan.