MAXIMUM ASS

I used to write plays. In a play, dialogue is everything. Almost nothing else matters. This fact was proven to me when I would try to put action into a play. I found that anything I wrote in a stage direction, unless it was indicated in dialogue as well, simply did not happen. No one ever pays any attention to stage directions. Seriously. I could write in a stage direction "He points a gun at her," and unless I included a line where she says "Don't point that gun at me!" nobody would ever point a gun at anybody.

(This goes for scene description as well. I once wrote a play that took place in "an empty room." I showed up on the first day of rehearsal to find a set that looked like the set for The Mary Tyler Moore Show. The set designer took "an empty room" to mean a room with tables and chairs and a sofa and a nice rug on the floor and nice pictures on the wall and a cunning ceiling lamp. So in addition to writing the action of the play into the dialogue, I took to writing the set description into the dialogue as well. "I can't believe how empty this room is! There isn't a stick of furniture in it!" and so forth.)

--Todd Alcott, " Screenwriting 101 -- Some Thoughts on Dialogue"