Frank Capra (1897 – 1991), director of the film It's a Wonderful Life, was famous (or infamous) for his improvisational directing style. He often walked onto the set with no more than the master scenes written. Capra explained his reasoning:
What you need is what the scene is about, who does what to whom, and who cares about whom ... All I want is a master scene and I'll take care of the rest – how to shoot it, how to keep the machinery out of the way, and how to focus attention on the actors at all times. (Wakeman, 1987)
This style worked both for and against the lead actor, Jimmy Stewart. It's rumored that Stewart was very nervous about his scene on the phone with Donna Reed because it was his first screen kiss since returning from his service in World War II. Capra filmed the scene in a single, unrehearsed take and it worked so well that part of the scene was cut because the censors deemed it too passionate!