There is no way to aim a pistol grip shotgun unless you attach a laser to it.
Now, that's just not true. You hold it up to your eye and then you pull the trigger...oh. Yeah. Well, when you get out of the hospital you always have another eye.
You point a shotgun and aim a rifle if I recall correctly.
A weapon light such as a SureFire attached to a pistol-grip shotgun will show you where the pattern will hit. Also who you are aiming at.