Help! I have an informational interview/sit down session with a manager at my work. He just stepped down from a district manager position in a field I'm very interested in working in.

The problem? I have never done an informational interview before! I kind of emailed him out of the blue, because I'm ready to move on with my career, but don't know where to start. Hmm.

What kinds of questions should I ask? I'm going to do some internet research of my own, but I figured I'd do some crowd sourcing here as well. Any advice would be gratefully appreciated.