Regarding how or where, the specifics and actionable advice is often domain specific, so if you have more details I would be glad to comment. As to interviewing potential users/customers if they will use your product, from personal experience I can say be wary about overweighting based on small sample size, and also be guarded against taking as proof of concept the assent of friends, family, or even non-anonymous users who would be incentived to provide positive feedback (even if subconsciously). For initial adopters, privilege "action over talk" in your decision calculus. Best of luck!!