I say that because of course you need to be careful with commercially sensitive ideas, as you do not want to pass your plan on to someone in the pub who then starts your idea before you across the road.
Whether it is travel, study, cooking or any other activity involving a process, planning is usually the first step. The same holds true for business. Business plans are probably more important than the business itself. For example, the plan for a house is more important than the house itself, though it is the house that people remember and not the plan. But the house wouldn't stand without the plan, would it?.
I teach that you should seek to learn from competitors; obviously never copy another business's idea or what they are doing, but you can absolutely learn from their mistakes or see what they are doing and discover ways to improve it. All of that analysis belongs in your business plan: make sure you have your competitors under the microscope and make sure that is a solid chunk of your plan. That is some of the best research and information you will gather about what will make your business successful in future.
Be Prepared For Risks : It is a fact of life that any new business or enterprise has a degree of risk attached to it. Therefore it is important for your business plan to analyse and calculate that risk, showing how you will engage with it. There is no business plan out there that is risk-free, but very often where the risk is higher then the rewards will be as well.