Interviewing people is both a science and an art. On the one hand, you want to maintain professional decorum and journalistic best practices by never misleading or lying to your sources to get the story, as well as never confusing your role as a journalist with that of a friend. On the other hand, however, we are human beings, and the journalist-source relationship is just that: a relationship.
So, when interviewing someone who is cooperative but maybe not as forthcoming with information as you’d like, your best bet is to rely on good old-fashioned interpersonal skills. This really goes for almost any interview, but there are times when it’s especially useful for drawing commentary from a source.
What does this look like? Simple: Be friendly, ask follow up questions, show genuine curiosity and a desire to hear more. Be an active listener. Make eye contact. When necessary, take your time; don’t rush your source. Recognize what information is being omitted and ask open-ended questions to get to that information.
To the latter point: Closed questions are ones that either don’t give the source cause to elaborate, like yes/no questions, or questions that basically put words in your source’s mouth. For instance: Don’t you think the fish here is overpriced? Or: As a Republican in New York, you must get frustrated a lot that most people here don’t share your politics.
Neither of those questions will lead to an interesting, honest answer, because you’ve steered your source in a certain, predetermined direction. Better questions would be: What do you think of the fish prices here? And: Tell me about your experience as a Republican living in a blue state like New York.
If none of those tactics work, you may just have a dull source on your hands, and it may be time to find another one. But if you really need that source for your story, employing the tactics described above should at least, and eventually, uncover something useful.