One key component critical to your success is scoping the competition. A business plan consultant studies the area where you will be located quite thoroughly. For example, if you plan on setting up a coffee shop on Main Street, or within the vicinity, the small business consultants you consult with will inquire about the number of existing coffee shops and the services they provide.
While these are easily available online, some of them are way better than the others. A lot depends on the approach that goes into writing the business plan.
After doing this, they will give recommendations based on what they find. If there are coffee shops already in place, one recommendation they might make would be to include free Wi-Fi as a way to bring in more customers.
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.