When I was an young venture capitalist, I worked for a former investment banker (his managing director to my associate and, later, principal). I both hated and loved him (Note: hyperbole, but truthfully, the former > the latter). Of the several pieces of great advice he gave me, the greatest lay in the formation of a question to a prospective investee.
Ask questions that require the investee to expound on response requiring many, many words:
You learn more from these kinds of questions that yes-no ones.
The responses will lead you to ask more questions.
When you do ask a question for which the answer will a "yes" or a "no," be very precise in your question.