You can learn a lot about people if you pay attention
When Mike Leigh asked me to cast Topsy-Turvy in 1996 I had only cast three films before. I couldn’t believe my luck. I also thought he must have gone insane, as I was very inexperienced, knew nothing whatsoever about Gilbert and Sullivan or actors with musical skills, or much about anything really. But I worked very hard and tried to soak up as much as possible from Mike and his encyclopaedic knowledge of actors, and from musical director Gary Yershon. I also met loads of actors and tried to learn about who could really do what. That all helped and I ended up being very proud of my contribution to that film, though still a bit embarrassed about all the crying I did in the musical auditions.