I have posted earlier on legendary editor Walter Murch whether it be his new work as an editor on "Jarhead" directed by Sam Mendes, or his role as an educator in a new book, "Art of Editing Film" by Michael Ondaatje. NPR has an excellent article on Murch with various scenes from his films and also has a nice snippet from the book. If you do not plan to buy the book, I suggest you read the article.

Here is a little taste, Murch says "There are underlying mathematical influences that determine how a film gets put together, which are amazingly consistent, seemingly independent of the films themselves. Over the years, I've come to rely on these influences -- navigation points -- as I work on each film. For instance: 2.5 -- an audience can process only two and a half thematic elements at any moment; 14 -- a sustained action scene averages out to fourteen new camera positions a minute; 30 -- an assembly should be no more than thirty percent over the ideal running length of the film. But these are perhaps just islands above a larger submerged continent of theory that we have yet to discover."