This film doesn't really have any storyline to speak of. Basically it is an episodic comedy-drama, set in New York in the late 60s, revolving around three friends as they try to avoid being drafted into the Army and sent to Vietnam, while experiencing various elements of the late 1960s counterculture.
The film uses a a style very reminiscent of the French "Nouvelle Vague" films, such as hand-held cameras, on-screen captions commenting on the action and speeded-up film.
The film is probably most well-known today for marking an early appearance by Robert De Niro (here aged 24) as voyeuristic amateur film-maker Jon Rubin, and for being an early film from director Brian De Palma.
The film is, luckily, worth watching for much more than this though. It is an interesting snapshot of it's times and, although very dated, it is often quite funny. The main problem is that the film hasn't aged very well and there's no structure to it, many episodes by far outstay their welcome.