A business that makes sense and is going to be sustainable in the future is one that has that clear vision within which all the smaller parts contribute to make it successful.
Before the preparing the plan, the entrepreneur should: Review previous business plans (if any) and their outcome. This review will help highlight which areas of the business have proved difficult to forecast historically. Be very clear as to objectives on which their plans will be based. Set out the key business assumptions on which their plans will be based.
The first point to keep in mind about business plans is... have a business plan! This may seem obvious but is overlooked. Many people start businesses without a plan; sometimes it can come from sheer bravado, thinking "I don't need a plan", or alternatively you might hear "It's all inside my head, that's my business plan".
I say that because of course you need to be careful with commercially sensitive ideas, as you do not want to pass your plan on to someone in the pub who then starts your idea before you across the road.