Who are your direct and indirect competitors? You really should gain at least an initial understanding of who else is offering similar products or services to your target market. It's good to know how their products or services are currently used and perceived _ why people buy them, and why they don't. In doing so, you begin to understand the strengths and weaknesses of your competitors from the consumer's perspective. Depending on what your product or service is, you can find all kinds of information about user experiences with your competitors' offerings. Sites like Amazon let you see product reviews by customers who bought products.
Developing Planning Modules: Compartmentalizing your plan by developing planning modules or "chunks" allows you to attack the plan in parts, yet still maintain a cohesive plan. I have found that developing an annual plan made up of quarterly targets _ thus becoming a rolling quarterly forecast financial model _ allows for a cohesive structure along with the nimbleness to react to market conditions. At the end of each quarter, a true_up process to align results to annual targets needs to be re_forecast and adjustments made.