Ask HN: Best question to ask business owners?

I work as a consultant, and semi-regularly have the opportunity to interface one on one with many small business owners. I realized that since I would like to start my own business one day, that I am wasting a golden opportunity by not asking at least a simple question of the owners. Even something as simple as "So how did you go about starting your business?" is better than nothing. How can I make the most of these opportunities? These are people that I have built a good working relationship with and would feel comfortable asking such questions.