Continuity mistake: When Jules is leaning against Michael's hotel door she is smoking a cigarette. When he opens the door she falls back and ash from the cigarette falls on her hair. Two shots later it is gone and her hair is rearranged while she is still on the floor. Then the ash reappears a few shots later.
Continuity mistake: Toward the end of the movie, Jules is yelling for Kimmy in a public restroom. When she walks in, her curls in the back of her hair are loose. Another shot shows her curls tight, and later they are back loose again. This actually happens repeatedly throughout the movie. With Jules's long, curly hair, it's obvious when it changes.