As you can see hanging a door is rather easy. The key is to make sure the door is plumb. In the video, the rough opening is square and plumb, and only a half inch wider than the door jamb. Of course this is the best case scenario. Often times, in older houses, the rough opening will be out of plumb and square. So, like the video shows, plumb the door by itself and don't fit the door to the rough opening.