1. How did you get on the right track?
  2. Did you have an aha! moment? What happened right before and right after? Can you recreate that mental state?
  3. When did you know you had the answer? How did you know that you did?
  4. Are there other ways to solve the problem?
  5. In hindsight, how would you have liked to have solved the problem?
  6. Can you describe the problem & solution simply & intuitively to someone else?