A business plan should be detailed. In listing your products and services for example, you should not really stop by just enumerating them. You also should write down the descriptions and scope of your products and services, touch base on production and identify means on how you can market your "brain - child" to your targeted niche.
It needs to have a list of everything you need. Note that the word everything here comprises of the equipment, technology, raw materials, financial and other resources that you may need when starting and running your business venture. Having all these listed will give you an idea on how much capital you need before you start and how much money should you make in a day to make your business survive.
Traditionally business plans have been highly confidential and quite limited in audience. The business plan itself is generally regarded as secret. An open business plan is a business plan with unlimited audience. The business plan is typically web published and made available to all. In the free software and open source business model, trade secrets, copyright and patents can no longer be used as effective locking mechanisms to provide sustainable advantages to a particular business and therefore a secret business plan is less relevant in those models.
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.