Edited excerpt from 8 Tips For Conducting Interviews That Deliver Relevant Customer Insights by Benson Garner:
Adopt a beginner’s mindset
Listen with open ears and an open mind and avoid interpreting customer responses too early.
Get facts, not opinions
Ask questions that get your customers to share facts and experiences rather than questions that result in opinions. Don’t ask “Would you..?” Ask “When is the last time you..?” or “Tell me about a time when you..?”
Ask “why” to get real motivations
Ask “why?” frequently. You might ask “Why do you need to..?” or “Why is ___ important to you?” or “Why is ___ such a pain?”.
Don’t mention solutions too early
It’s easy to fall into the trap of offering your solution during learning interviews. Don’t do it. People inherently wish to please others so it’s only natural that they confirm your opinions.
(1) On “Don’t ask Would you..?”, see The survey question you should never ask.
(2) Cf. Product discovery questions to ask potential customers.
(3) Cf. How to ask great questions.