This is a great and very common concern. The key is to shift from asking for opinions to investigating real behaviors and experiences. Start by planning a discussion guide with a clear arc: begin with broad, open-ended questions about their life/work context related to your product domain ("Tell me about the last time you..."). This establishes rapport and reveals their mental model before you bias them. Always pilot your interview script with a colleague first. For a comprehensive, step-by-step guide that covers planning, conducting, and analyzing interviews with concrete examples, I highly recommend this definitive resource on UX user interview techniques. It breaks down the entire process from writing questions to synthesizing data.