1/ The goal of the call should be to learn about the user and their problem—not to talk about what you’re building.
2/ Avoid asking users what they want. If they do describe features they’d use, dig deeper. Get to the core problem by asking them exactly why they want that feature, how often it comes up, etc.
3/ Resist the temptation to talk a lot. Ask a mix of broad & specific questions, and then listen.
4/ Iterate on the format! Reflect on which questions give you the best answers. Replace questions that consistently yield unhelpful answers.