In this Ted Talk, Mike Dronkers gives tips on conducting interviews that put subjects at ease while engaging them with curiosity and research skills.
Before the interview, Dronkers emphasizes that research is the key. Get to know the interviewee by watching their previous interviews. Use what they've said previously as a jumping-off point and study their small verbal and nonverbal cues to know when they're relaxed or uncomfortable.
Use research to discover valuable positive nuggets of information during the interview so the interviewee can happily respond, "wow, how did you know that?"
Most importantly, Dronkers emphasizes being curious about what the speaker has to say, especially with the new and uncomfortable. The key to getting the conversation you want to have is being as invested and interested in everything as possible. The dialogue will be more open, honest and revealing, and much more evocative than answering routine questions.