Defensive accuracy is being able to hit an 8.5" x 11" piece of typing paper at seven yards with your firearm. This is possible if you can see the front sight within the rear sight. If you practice with a smaller target, this becomes even easier and more natural.
This video tutorial will show you how to improve your handgun defensive accuracy by shooting shotgun shells. If you can hit a shotgun shell with your pistol, chances are you can hit a human when you need to, in self-defense of course.
Remember three basic safety rules; always keep the gun pointed in a safe direction, always keep your finger off of the trigger until you are ready to shoot, and always keep the gun unloaded until ready to use.