Design a customer interview framework for [COMPANY/PRODUCT STAGE]. Research objective: [DESCRIBE — validate problem, improve onboarding, understand churn, etc.]. Who to interview: [CUSTOMER SEGMENT]. Provide: 1) Screening criteria and recruitment message, 2) Interview guide with 10-12 questions (open-ended, no leading questions), 3) Probing follow-up questions for the most important answers, 4) What to observe and listen for beyond the explicit answers, 5) How to take notes without disrupting the conversation, 6) Synthesis framework for finding patterns across interviews, 7) How to turn insights into product/marketing decisions. Common mistakes in customer interviews and how to avoid them.