10) Clean up after yourself. A stage manager has a million things to do more important than picking up your half empty water bottles, but if you don't pick up after yourself, they have to do that, too. Want super-extra brownie points? Pick up after other sloppy cast members, or remind them to do so.
I will always love and adore a particular actor I worked with two years ago. We were in four different rehearsal spaces, sometimes all in the same day, and after a week of taking five minutes, every time we moved, to clean up water bottles and candy wrappers, I issued a lecture about respecting rental spaces, cleaning up after yourself, the fact that I would also like a break when we moved shop, but I can't take one if I'm cleaning up their trash. Out of a cast of five, ONE picked up his garbage, and everyone else's from that point forth, AND asked if I needed help with anything. I'd work with him again, on any project, in a flat minute.