The film accurately shows Charles Manson ( Damon Herriman ) visiting Tate's house early in the film, looking for music producer Terry Melcher (the previous renter) because he felt that Melcher owed him the record deal that he was once promised. After learning that Melcher had moved on, Manson decided that it was still good location because he had been in the house before and he knew the layout of the main house very well. (He was unaware, however, of the guest house in which a groundsman lived; one who later said that he had not heard the screams but whose visitor that night had been the first to be killed).
Six months later Manson instructed four of his followers to go to the house and to kill all the occupants. The four drove over there, briefly parked on the driveway to cut the phone lines to Tate's house, then proceeded to park the car at the bottom of the hill, went back to the house on foot and killed five people (Tate, three of her friends who happened to be at the house, and the friend of the groundsman who had responded to a personal ad for a radio for sale).
The first significant point of divergence between the real and fictional account is the fact that Dalton notices the four as they are parked on the driveway. He gets out, verbally abuses them and sends them away. This angers Tex ( Austin Butler ) and the three women to the point where they decide to come back and invade Dalton's house instead. This incident also causes the woman called Flower Child ( Maya Hawke ) to get cold feet, and leave with the car (in real life, this was Linda Kasabian, who accompanied the others all the way but did not participate in the killings). In the end, the fatal mistake on the part of the killers is invading Dalton's house, not counting on the resistance of Booth and his dog, and Dalton himself. Flower Child was played by the daughter of Tarantino favorite Uma Thurman.
Before making a huge impact in Smokey and the Bandit (1977), Reynolds had spent many years kicking around in TV shows, mostly playing villains and his career was going nowhere. Tarantino based his film on his experience growing up in Los Angeles in the sixties and seventies. Reynolds did not leap from obscurity until Tarantino was 14 years old. It is interesting that Dalton supposedly played the bad guy role in the featured episode of The F.B.I. (1965) - a role that was played in real life by Burt Reynolds.
When Rick is talking with Trudy he says that in fifteen years she would be washed up as well as him. Kurt Russell was one of an extremely small number of child stars who continued to have a strong career through adulthood. In fact, he was the only one to end up with high-profile roles into his senior years, having made this particular film at the age of 68.
The opening scenes show two good guys responding to a late-night horse theft and riding off without cowboy hats, making the audience wonder if this was present-day. Presumably Wanamaker rationalized this hatless aspect as depicting haste, yet he forgot about how this might be interpreted by an audience. Also, they were both wearing plaid shirts, with was also odd. Plus much of the camera work, angles, sudden zooms and the like were very strongly influenced by TV detective shows of the day. These were reflections of Wanamaker's personality, which no doubt were noted by Quentin Tarantino when scripting and directing the Wanamaker portrayal.
It might also be noted that Leonardo DiCaprio's scruffy, shaggy-haired, mustachioed hippie-villain in this film was very closely modeled on the look that Wanamaker designed for the original actor, Joe Don Baker.