Start by writing a description of your business, including what stage of development it is currently in (conception, start_up, first year, mature, exit) and your plans for growth. Discuss the nature of your business, the main products and services you offer, the market for your products and services, and how and by whom the business is operated.
This part of the plan details the features and benefits of your products and services, their seasonality and life cycle, as well as any future products and services you are planning. It also includes a thorough market analysis, in which you will study your customers, your competition and the market itself. Here you should include a PEST analysis, in which you will consider the impact of various factors upon your business. The factors include combinations of the following, depending upon your business: social, technological, economic, environmental, political, legal, ethical, and demographic.
Business Description: 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 company's mission statement, goals and objectives, business philosophy, as well as its legal form of ownership (sole proprietor, corporation, LLC, etc.).
Do not try to write your business plan in one sitting. As I mentioned in the beginning, for a traditional brick and mortar business, it could take in excess of 100 hours to compile all of the information needed into a comprehensive but yet understandable document. For online businesses, probably not that long. But your final product should be well thought out, well documented and easily understandable.