Continuity mistake: When Val and Earl are being chased by the graboid in the first shot it appears that the graboid is going perpendicular to the fence (you can see this because of the wires that cross it). But in the next shot the graboid appears to be going parallel to the fence. (00:33:20)
Continuity mistake: When they all are trying to lure the graboids away from Val, Rhonda looks down the pipe running down the from the water tank. A piece of cloth soaked in water is tied around the pipe and water is dripping from it. When it cuts to Rhonda climbing down the water has stopped dripping. (01:08:45)
Continuity mistake: When the snakeoid is chasing Val and Earl after they lose their horses, they run along a fence and the monster causes all the fence posts to fall over backwards. But shortly after, all the fence posts are seen to be upright, although some are tilted a little to the right.
Continuity mistake: When Val and Earl are relaxing with a couple of cold ones after they bury the trash, Val's recliner chair changes. From the side it is a brownish-rust color cloth material. In the next shot, from the front view, it is greenish leather. This scene takes place after Rhonda's near miss with the graboid but before the first guy, old Edgar, is found dead.
Continuity mistake: Reba gets out of their truck at the compound and looks through the binoculars - in the foreground you see the tractor and trailer they use to escape are very close together, or are attached already. When Kevin Bacon and the other guy figure out to use it, the camera pans around and the tractor and trailer are 60-100 feet apart.