A business plan is a formal statement of business goals, reasons they are attainable, and plans for reaching them. It may also contain background information about the organization or team attempting to reach those goals.
Identify your audience. A good business plan should be written from the prospective of the audience. First, you need to decide on the purpose the plan. Are you trying to persuade an investor to take on your project or communicate the future plans for the company? The purpose of the business plan will affect the style and content so make sure you are clear on this before beginning. A good business plan needs to be tailored to the specific requirements of the target audience in order to be engaging.
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.
Attention to detail. A plan that is concise and clear reads professionally so don't make yours too wordy. The reader needs enough detail and information to be able to make an informed decision. As with all professional documents, care must be taken to avoid spelling mistakes and use correct grammar and punctuation. A plan that makes absurd or unrealistic assumptions is of no use so stick to the facts and make sure you are making credible projections and accurate content at all times.