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.
The primary difference between profit and non-profit organizations is that "for-profit" organizations look to maximize wealth versus non-profit organizations, which look to provide a greater good to society. In non-profit organizations, creative tensions may develop in the effort to balance mission with "margin" (or revenue).
Do your research. In order to be able to write a strong, comprehensive business plan you need to possess a sound knowledge of the market you are involved in. You need to actively conduct market research and ensure that your plan makes reference to your findings. It should include factors such as market size, the predicted growth path of said market and how you propose to gain access to it. For example, if you are planning on opening a bar then your business plan should include figures based on the local population, cost of suppliers, predictions about whether the bar industry is likely to grow or decline in the area and a review of the competitive environment.
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.