Continuity mistake: When the Terminator's chopper breaks through the gates of the reservoir, they sound as if they crash against the fence, yet a frame later, from the angle in front, the gates are open wide and still.
Continuity mistake: When escaping out of the parking lot, John drives past the same blue pick-up truck twice.
Continuity mistake: During the truck scene, when the truck has just come off the bridge, notice the sign on the right hand side says "24 hours." Seconds later the sign seems to have mysteriously disappeared.
Continuity mistake: During the pool fight scene, you can see there's an orange ball next to the upper left pocket. In following shots it's no longer next to it and it has a dark ball in front.
Continuity mistake: John Connor comes out of the parking lot and appears right in the middle of the truck's lane, making the driver swerve to his left. From a close-up, the driver turns the wheel and straightens the truck and keeps on driving, but the following wide angle shows the truck swerved and the driver straightening it again.