Do you have a formal business plan with budgets, market research, marketing plan, etc. or do you simply have an idea that you work on, hoping that somebody will like what you build?
Personally I write concept papers that discuss what the product is, why it is great, who will use it, and a rought sketch of where the money will come from.
What do you do ?
This may sound strange, but I use the first page of my website as my "business plan". No sense working on anything else until it answers all of these questions in an instant.