Skillful interviewing for documentaries involves more than good conversation. It requires understanding the purpose of the movie, eliciting from people their piece of a story that will be woven together with the other elements. Of course it requires good listening and attentiveness to that spontaneous moment. It also requires good preparation so as not to be an endless ramble. And it requires framing questions that help the person deliver.
As an example of interviewing, watch this clip from an orientation video for deputies to the 71st General Convention of the Episcopal Church. I believe it shows mastery of some complex and dry content yet tells a compelling and moving story through good interviews.
Other examples:
Short video describing the work of The Salvadori Center; interviews with thoughtful kids ages 7-12.
Informational video for college students considering a semester -- in the US or abroad -- of service learning experience
Fund-raising documentary for the Episcopal Church. (Emmy nominated)
People from all walks of life reflect on why they read the bible.