Hughes’ method of shooting comedy has become virtually an industry standard. He’d often let the camera roll through four or five takes in a row, looking for the right tone and rhythm for a scene. “He loved his actors and loved language, so he’d shoot a lot of film,” says Jacobson. “It became a big thing in comedy after John did it — listening to the actors and looking for those great moments. John would hear a line and get the actor to go with it. It really wasn’t the actors who were improvising. It was John improvising.
Source: adamiss