At the beginning of the movie, when Wes is practicing in the barn with his 6 shooter, he fires 8 consecutive shots without reloading.
At about 30 minutes in, when Hardin returns with a wedding dress to marry Jane, she removes the glass chimney from an oil lamp to blow it out. Everyone knows that the glass of an oil lamp, that is burning, would inflict severe burns to your hands and the proper way to extinguish it is to place a hand just behind the chimney opening and blow it out or just turn the wick down to snuff it.
Mid-point in the film, as the wounded Hardin is being helped into hiding by his uncle, a two-trailer truck drives by in the background, clearly visible.