Have An Overall Vision : When writing your business plan it is really important to have an overriding vision of what your business is going to do, what it is going to be, and what you want to achieve. Very often it is tempting to get straight into the technical details, the monetary concerns, financial matters, where you will be sourcing supplies, etc. Now all these things will be vital in your business plan, but it has to be held together by a coherent, broader vision.
However, business planning is an ongoing process and it should be updated regularly to assist in forward planning, the challenge for the entrepreneur while preparing a business plan is to communicate his ideas and identify gaps in management information about their business, competitors and the market.
Research Your Competitors (But Don't Copy!) Every business plan should focus a lot on the business's potential competitors, because research and analysis of the competition effectively gives you plenty of useful information. It may guide you as to where you should be advertising and marketing, or certain strategies to use or ones to avoid because you see they have been used unsuccessfully by others.
When I have received business plans, the very best responses come from people who have looked at the risks and have an answer for every question. What you never want is to throw a scenario at your plan and have to answer "I don't know what I would do in that situation". You want to plan for every possible contingency, and certainly all the major risks to the ongoing success of your business.