To conduct a good research-focused interview, you need to cultivate a professional interviewing mindset.

Steve Portigal has been doing this for years, and he has written a book to help other researchers and designers conduct better interviews.

Now in its second edition, Interviewing Users: How to Uncover Compelling Insights, covers interviewing techniques, of course, but also research best practices, how to document your work, and how to make sense of your discoveries.

https://ellessmedia.com/csi/steve-portigal/