Rules in a communicative class

What rules should you have in your class if you want it to be communicative? What if you're teaching using TPRS?

In my class, these are my rules:
1.) Watch.
2.) Listen.
3.) Tell me when you don't understand (even if it's a hand signal, which in my class is an X made with your fingers, hands, arms, whole body, whatever).

And when we do a song, my mantra is "You can watch and listen or you can watch and sing, but you can't..." (and all the students say "NOT WATCH.")

Make your rules create an environment friendly for language acquisition.