Business plan to some may sound stupid but it can be very handy. This is marketing planning which is mentioned but over all planning. Anyone may see it as. Waste of time etc. "I know what I am doing start small be big" but planning your way there is the key. It allows you to see issues in the market or in your idea and how you can avoid it later down the road.

Personally its worth looking in to.... what you got to loose?