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.
Include details about all of the following that are applicable to your business in the marketing section of your plan: location and distribution, and promotional strategies, such as packaging, public relations, advertising, and customer service. As a result of exploring these areas, you will naturally need to consider how much you will budget for your marketing efforts. This question is closely connected to your sales forecast, which leads us into the next section of the business plan.
Understand gaps and weaknesses within the plan. Any casual viewer of the BBC programme, Dragons Den will be aware of how easy it is for weaknesses or gaps to be identified. Depending upon the purpose of the plan, this may, or may not, prove to be critical. It is often easier to recognise such weaknesses and gaps, and be prepared to deal with them, either by noting them in the plan itself, or having appropriate answers available should the need arise.
I suggest that you construct easy to read tables and graphs for the financial portion of the plan. The worksheets suggested are: Salaries/Wages and Benefits, Outside Services, Insurance, Advertising Budget, Occupancy Expense, Sales Forecasts, Cost of Projected Product Units, Fixed Assets, Growth (or Start_Up) Expenses, and Miscellaneous Expenses. You may find some of the worksheet templates at PlanWare.org to be useful.