Compartmentalizing your plan by developing planning modules allows you to attack the plan in parts, yet still maintain a cohesive plan. I have found that developing an annual plan made up of quarterly targets - thus becoming a rolling quarterly forecast financial model - allows for a cohesive structure along with the nimbleness to react to market conditions. At the end of each quarter, a true-up process to align results to annual targets needs to be re-forecast and adjustments made.
After the executive summary, you need to write a short description of the business you are going into. You need to give a general description of the industry your business belongs to. You will write about your companys mission statement, goals and objectives, business philosophy, as well as its legal form of ownership (sole proprietor, corporation, LLC, etc.).