2. His Work Ethic
And of course any Lumetian fan knows that the director was quite prone to full-scale rehearsals with his actors, carving up the script with the screenwriters, and getting down to the nitty-gritty before the cameras ever started rolling. His experience as a theatrical director aided this, as he had a desire to reach into the core of the characters and stories, which meant a full-out exploration before filming ever took place. While his book goes through this process more intimately, I'll provide the IMdB summation: "On all his films he assembles the cast for a two week rehearsal in which they perform the script from beginning to end like a play. This cuts down on the need for repeated takes during filming." There's a method to the madness, of course, and Lumet didn't want to waste any time. As a filmmaker, he was incredibly conscious of budget restraints, so he started from scratch with the basic players and worked his way from there. Not only was it financially conscious, but it also provided the necessary outlet for him to pull out the performances (or at least the rough versions of them) from his actors that he was seeking for the film.
" Im finding out things about the actors. What stimulates them, what triggers their emotions? What annoys them? Hows their concentration? Do they have a technique? What method of acting do they use? The Method made famous at the Actors Studio, based on the teachings of Stanislavsky, is not the only one. Ralph Richardson, whom I saw give at least three great performances, in theatre and film, used a completely auditory, musical system. During rehearsals of Long Days Journey Into Night, he asked a simple question. Forty-five minutes later I finished my answer. Ralph paused a moment and then sonorously said, I see what you mean, dear boy: a little more cello, a little less flute. - Sidney Lumet, Making Movies
http://youtu.be/qwsrKRo5gdA