But your idea may be so new that you may also need to talk to potential customers, host some focus groups, talk to an ad agency, or maybe even make a prototype and float it past some people. Be prepared to spend the time. Remember, it's not about the Plan but the Planning.
Carrying on with the example of a coffee shop, a business plan consultant will figure out what the best location would be. They already know coffee shops do well in areas with a certain demographic in place. These include students and workers, who are within close proximity to book stores.
Maybe it's okay as an assignment for an MBA class, but it would be just too confining and irrelevant for today's fast-paced business environment. Anyway, you're ready! You've thought about this business venture for a long time and talked it over with friends and everybody agrees it's a great idea. Best to strike while the iron is hot!
Apart from this, they also analyze consumer trends and gather legislation reports and regulations that might have a future impact on your particular venture. These expert individuals make it their responsibility to build upon previous experiences and the requirements needed for you to carry out your intended plan.