A lot of resources nowadays provide ready-made plans for specific businesses and whilst this is handy, most business owners will recommend that you write the plan yourself. This is because writing a plan for your business actually forces you to focus on what you want from your business and how to achieve your goals. When looking back on your initial plan for reference, you shouldn't necessarily assume that your initial assumptions and predictions will be correct, they are just that: predictions. You should be able to go back to your plan on a regular basis and view it and change it to relate to the actual current situation.
Remember that each section in your business plan will overlap. This means that you may cover information more than once as you move from section to section. This is okay. Your business plan may be considered as a whole or may be viewed as individual sections. This means that each section must include all key information. Don't neglect including important information simply because you feel it has been covered in other sections.