[iforgotmypass]

There's a nice iterative process called Customer Development from the Lean Startup methodology. Use this to validate your initial assumptions, to fine out the Business Model (Value Proposition and the target audience) and generally understand pain points of your potential customers (how much does the problem currently cost them, how they solve it currently, what are the possible alternatives, etc.).

Hard to give a complete advice im just a few sentences, but basically this framework gave me the understanding necessary to quickly build out (validate) business ideas before anything is really developed. To oversimplify it - try selling before building it. That will give you a very good understanding of the potential market size, the actual needs of people and so on.