Even if your business has been going a long time and is working as you want it to be, there are still benefits in updating or creating a business plan. There is no set way a business plan should be written or laid out but it should always include: a summary, description of your business, market research, marketing & sales strategy, details of your team/staff and financial forecasts.
There are loads of business plan and goal setting resources and templates available online, but one thing to remember is that everyone is different. A template may not be applicable to you and your business.
Mapping out your business plan will require lots of thought and research. The areas you need to look at include:
Start off by making notes on the above subjects, maybe allocate a page in your notebook to to each point and jot down whatever comes into your head. Now your business plan is in its early stages, it is a good idea to get feedback from people you know. This third person prospective could point out areas that you have missed and help you develop what you have already planned out.
Now you have your basic draft plan, it is time to get to work on creating your actual business plan.
Here are some helpful resources to get you on your way:
http://www.smarta.com/advice/business-planning/business-plans/how-to-write-a-business-plan
http://www.cida.co.uk/factsheet/how-to-write-a-business-plan/