Customer interview script

Help me prepare an interview with a potential customer to find out whether they have the problem I want to solve. Follow the approach of Rob Fitzpatrick's book "The Mom Test": we ask about past behavior, not opinions about my idea.

Idea: [what I want to build]
Who I'm talking to: [the person's role and situation]
What I want to learn: [the main unknowns]
Length: [20 to 30 minutes]

Prepare:
1. An opening of 2 to 3 sentences: why I'm calling, that I'm not selling anything, and how long it will take.
2. Ten to twelve questions about past experience: the last time they ran into the problem, how they handled it, what they tried, what it cost in time and money, and what annoyed them. No "would you buy" and no "what do you think of the idea."
3. For each question, 1 to 2 follow-ups (such as "What happened next?" or "Why was that important?").
4. Signs of a strong signal (already paying or spending hours, looked for a solution on their own) and of a weak one (compliments, "that would be cool," plans for the future).
5. The close: which next step to ask for, such as a referral, a pilot or a pre-order.
6. A note-taking template: verbatim quotes · current solution · costs · how serious the problem is, 1 to 5 · next step.

Separately: 5 mistakes I might make in this interview and how to avoid them.