A business plan comprises information from different disciplines and it is unlikely that one single person will be able to provide all the answers to the questions posed in there. SMEs have more advantages than startups, because all the different departments (financial, production, sales and personnel) will provide information according to the growth hypothesis formulated. 

In the case of a startup, internal resources can be insufficient. In this case, we may look for external contributions (consultants or leaders of the sector).

It is important that all members of the project agree about the aims and objectives of the plan, and make a commitment about its content. As in any project, the basic needs of the plan may be communicated to all members and terms have to be fixed to collaborators. This technique of "previous spreading" will provide great advantages further on. And, moreover, it reduces critiques and the "corridor policy" that can ruin the project in the first presentation.