Star Wars began filming on March 22nd 1976 in Tunisia.
All external Tattooine scenes were shot in Tunisia, with Mark Hamill and Alec Guiness being the only principal cast members. This shoot lasted two and a half weeks.
The cast and crew then moved to Elstree Studios in England for all the on-set filming, essentially the entire rest of the film. This took 14 1/2 weeks, totalling 17 weeks (4 1/2 months) of filming.
Additional shots for Tattooine were completed in Death Valley in Arizona. As late as March of 1977 (two months before the film was released, and three months after it's initial intended release date of Christmas '76) a second-unit crew was sent to Tikal, Guatemala, to film the Mayan temples as the backdrop for the Rebel base. While filming in Tikal, the crew paid locals with a six pack of beer to watch over the camera equipment for several day