I think I possess this skill (at least partially), and the trick of "knowing what to ask" is to train yourself heuristics that guide you towards questions that

I think I possess this skill (at least partially), and the trick of "knowing what to ask" is to train yourself heuristics that guide you towards questions that reveal outstandingly large amounts of new information. Of course you have limited information, so those determinations about how much information a question's answer would yield are plagued by that. Hence the heuristics. This is not easy to learn, and great understanding ability is a prerequisite.