George Lucas, inspired by Francis Ford Coppola's The Godfather: Part II (1974) wanted to make his sequel darker and more complicated. Writer/director Bill Norton thought that cutting between four different time frames would be to jolting for most of the audience and also didn't like the various film formats used for each of the four story lines. Years later Lucas would admit that Norton was right.
George Lucas came up with the idea of shooting each of the four story lines in a different aspect ratio. Milner's Drag racing was in the 1950's exploitation style using a wide angle, stationary camera. The Vietnam sequences were shot on 16-milimeter film, like the TV reports of the time. Laurie and Steve's campus riot resembled a Hollywood version of student rebellions like The Strawberry Statement (1970) or Getting Straight (1970). Debbie's trip were in multiple-image split-screen, inspired by Woodstock (1970).
Producer Howard G. Kazanjian was asked by George Lucas to come up with a list of young California screenwriters to write the screenplay based on Lucas' outlines. When he picked Bill Norton, Lucas told him that if he did a good job on the script, he could direct the movie.
Since long hair was the fad in the late 1970's, extras were recruited from the California Maritime Academy in Vallejo, due to their required short haircuts, and their campus was close to the Marin and the Fremont Raceway filming locations.
An uncredited Marcia Lucas edited the split-screen scenes for the 1966 sequence (many of which were incorporated to cover up the story defects). George Lucas, also uncredited, edited the Vietnam scenes for the 1965 sequence, making footage of just two helicopters seem like a dozen.