Do you engage your market before or after you make a prototype?
I say it's better to get people involved as early as possible (before making the prototype), because not only will you make sure there's a real value but also there's less post development going on.
But, how do you go about approaching your market before having a prototype? It's much easier to get people involved when you have something going on (more than just a vision or an idea). For example, a prototype, something tangible, a proof of commitment, etc.