I'm re-reading the wonderful book The Filmmaker's Intuition by Judith Weston - if you haven't read it, it's fantastic, although I would check out her book Directing Actors first (it's on this site somewhere if you want to see what it looks like).
She had one paragraph that so succinctly described the director's job that I thought I should repost it.
"The film director's task is to tell the story. The tasks involved in telling a story filmically can be grouped thus:
1. Choose a script, and investigate and imagine its subtext story;
2. Supervise the design elements, and make sure they tell the story;
3. Plan and supervise the shots, and make sure they tell the story;
4. Cast the actors, block out their physical action, and make sure their performances tell the story."
She later adds, "There are two crucial directorial duties that many directors are clueless in carrying out: setting the blocking (physical movement) of scenes; and creating pace and tempo-rhythm... Rehearsal can be a place for directors to make these choices, thus preventing chaos and despair in editing."