“Shampoo” recounts an especially eventful day in the life of George (Warren Beatty), a Beverly Hills hairdresser and lothario who frantically runs around town on the eve of the 1968 presidential election trying to sort out his many financial and romantic entanglements. His attempts to scrape together the money to open his own salon are continually sidetracked by the distractions presented by his lovers — played brilliantly by Goldie Hawn, Julie Christie, and Lee Grant (in an Oscar®-winning performance) — and a new conquest in the person of teenage Carrie Fisher, who makes a memorable film debut. Beatty dreamed up the project, co-wrote the script with Robert Towne (“Chinatown”), and enlisted Hal Ashby as director, and the resulting carousel of doomed relationships is an essential ’70s farce — a sharp look back at the sexual politics and self-absorption of the preceding decade. Although released in 1975, “Shampoo” is an honorary member of SLIFF’s Golden Anniversaries program because of its 1968 setting. Also on the double bill is “Hal,” a new documentary on Ashby.