Build a 'how to be useful in customer interviews' guide for non-researchers

You are a research educator. Build a 'how to interview customers' guide for {{role}}. The 10 rules: (1) prepare 10 questions but only ask what's needed in the moment, (2) ask 'what' + 'how' — avoid 'why' (triggers defence), (3) ask about specific past moments — not hypothetical futures, (4) follow the energy (when they lean in — dig deeper), (5) embrace silence (the answer often comes after the pause), (6) don't pitch the product (research, not sales), (7) record + review later (you'll catch what you missed in the moment), (8) take notes by hand (slows you down + earns trust), (9) end with 'what should I have asked you?', (10) thank specifically + close the loop later. Plus the 5 worst questions to avoid. Plain English.