Other: When Harry, Ron, and Hermione go after the Philosopher's Stone, the harp stops playing. They look up at the dog, but its shadow is cast on the ceiling above them as well as on top of them. This shows there were lights behind the 3.

Continuity: In the chess scene, when Ron falls off the horse, he is lying on his side on the floor with one knee bent so that one foot is higher than the other. When Harry and Hermione run over to check on him, one foot is on top of the other.

Visible crew/equipment: During the chess game when the queen drives her sword through Ron's knight, if you pause it just right you can clearly tell that it's a stunt double falling off the horse.

Continuity: When Professor McGonnagall is talking to the children before their sorting, you can tell when the camera is on her that the lighting is candle-like (note the flicker). When the camera cuts to the children, there is no flicker (check out Hermione).