Any athlete, dancer, ballerina warm up before going out, because no one will work with "cold muscles". Singers sing before the concert, because no one sings with "cold ligaments". Actors usually limit themselves to articulation exercises to warm up the voice and diction and forget about the body. And muscles after sleep, if it's a morning show or after a long day, if it’s evening, also require charging. After all, your character can jump and run, dance and climb to the balcony. Do a little warm-up before going on stage, warm your muscles, but do not overdo it, sweaty Romeo is unlikely for Juliet.
Did your parents slap you on the back when you were a kid? And who will do it on stage, Director? No, please, that's your job. Watch your posture, keep straight and proud, unless you're Quasimodo.
Any movement on the stage should make sense. No gesture can be made for nothing. Therefore, if you are nervous, forgot the text; do not rush around the stage like a hunted animal, hoping to remember words. Improvise with the lines, but leave the body relax. Don't drive your colleagues crazy.
The people love your eyes. Look in the hall, communicate with look. Don't look at the floor and mumble the text under your breath. Sometimes the look is longer than a thousand words.
The actor on the stage must have a private space, if the role does not have close contact with a partner. Do not oppress and do not dislodge it, the stage is big; give him the opportunity for maneuver.
And, most importantly, how to start any drama club for kids in kindergarten: "Never stand with your back to the audience!" If you need to turn around, do it so that the viewer does not have to contemplate your back for a long time. The face is much more interesting.