It also needs to be written in formal format and style. You have to remember that a business plan is something that you may have to present to your business partners, financial firms and banks. So if you can, refrain from using slang in any part of your plan.
It should include a market research that identifies your competitors, their share of the market and the range of the products they produce. By learning how they conduct their operations, you may learn tricks of the trade in the business you want to enter and you also get to have a basis on what you can do to excel.
This situation is complicated by the fact that many venture capitalists will refuse to sign an NDA before looking at a business plan, lest it put them in the untenable position of looking at two independently developed look-alike business plans, both claiming originality. In such situations one may need to develop two versions of the business plan: a stripped down plan that can be used to develop a relationship and a detail plan that is only shown when investors have sufficient interest and trust to sign an NDA.
Once you have done all this you should have a complete and detailed professional business plan. The most important thing to remember when developing the plan is to see it as a living document and include specifics regarding dates and specific responsibilities. Your plan will need constant reviews and updates and things change so expect it to be a work in process for a good stretch of time. It will all be worth it in the end, a well-written plan will help ensure that the business is fully focused on what is required to achieve the company's goal.