A good director creates a playground for actors, and lets them go. The trick for a good director is in casting properly, and creating the playroom, and then they'll get stuff that they don't expect, and can't even direct. All the audience wants to believe is that whatever is happening, it is happening for the first time. They want to see the people within the work exchanging dialogue and action in that moment. There are not a lot of actors that can do that.
