The first time I ever did a rehearsal with real actors, I was terrified! All I kept thinking was, "They know I don't know what I'm doing, they know I don't know what I'm doing," and consequently I lost quite a lot of control on that particular film because I could not get a hold of myself. All a rehearsal is, is helping the actors familiarise themselves with the text and working out how you are going to portray the scenes. You are a guide as a director. You help the actors understand the characters, loose lines that don't work, give some insight into action and movement.
Actors are the life and soul of your production. You can't work without them, so don't be afraid of them. Love them. Appreciate them. I often sit back and just stare in awe at how actors bring those characters to life when I ask them to. How flexible they are (most of them) and willing to be vulnerable.
Here are a few tips for rehearsals from my experience that I wanted to share