Tack's vest rips open after he is punched off of the car by Hubbs. Later when he goes to the Jill's house to party, he is wearing the same vest, which is in perfect condition.
When Jill kicks Joe, he falls to his knees and she pushes him over with her foot. As he's falling over, you can see the imprint of his head and shoulder in the sand from a previous take.
When Crump's brother is breaking down the front door of the house, the door's chain switches between being latched and unlatched several times.
When the police are arresting kids at Jill's dad's house you see Hubbs car leaving in the back ground; and a little later they cut back to Joe and Hubbs getting in the car.
'90s and '80s era cars are clearly seen in the opening hitchhiking scene.
Despite being set in the 70s, there is a Michael's craft store seen in one scene, even though Michael's didn't go nationwide until 1984.
Some of the fashion worn by various characters in the movie are actually more reminiscent of 90s fashion (particularly grunge fashion) than 70s fashion.
Blue Oyster Cult's "Burnin' for You" is heard one decade too early in one scene.
Reflected in the microwave oven door in the kitchen scene.
In the scene where Frankie Avalon drives up to Joe and Hubbs, there is a beer can in the middle of the road that served as a marker for where the two drivers were to stop and talk.