Continuity mistake: At the valley party, after Travis tries to see how Tai is while she's laid out on the counter, Cher pushes him all the way out of the kitchen so that his entire body is in the doorframe. In the next shot, he is several steps back into the kitchen as he turns to go back into the other room.
Continuity mistake: When Cher's driving instructor tells her she failed her test, the instructor is sitting next to her, then we see a brief shot of Cher crying, then we see the instructor out of the car and at the front of it. The camera wasn't off him long enough for him to get out of the car and walk that far, and we didn't hear a door opening or closing.
Character mistake: Circus Liquor is actually located in North Hollywood, not Sun Valley (although Sun Valley is just a few short miles away from there).