What makes a great stage actor? We wish we followed these rules all the time when we act. The truth is, you really learn these things by doing it: "acting" means putting it all into action. Here’s a few tips from Niamh Cusack who has worked at the RSC, the National Theatre and the Old Vic London.
Trust your playwright. If he or she is a great one, most of the work will have been done for you. Read the play at least three times out loud before standing it on its feet. A lot of the blocking (the positioning of the actors on stage) will come out of understanding what your characters want, and from whom.
Listen to the person who's talking – unless your character isn't listening to them. Don't be afraid to make an eejit of yourself. Change the look in the other person's eye. If it's in verse, paraphrase it first. Keep it simple. Remember that most characters use words to affect, connect with or change the other person. Finally, always remember it’s only a play !