Some things which worked for me:

- Align on how he perceives success. It can be a framework or Metrics. This thing will help you always align with the person at any point of time. If the topic deviates, you can always use the success definition as a point to bring the discussion back to track.

- Having multiple perspective. This helps you build holistic thinking around product and builds confidence in the conversation - Engineering, Business, Finance(Unit economics), Marketing etc shows that you can work across the teams and structure