I find it sad, unfortunate, and somewhat annoying that so many American citizens seem so utterly baffled about something which should occur to them as both a natural instinct and a common sense situation.
I know I am not allowed to carry a gun in public because I don't have a permit. But I don't need a permit to have a gun in my home. So if someone breaks into my home while I am there, and I hear it happening in time, I am well prepared to defend myself against being harmed by the intruder.
But the fact I am equipped and prepared to disable or kill the intruder does not mean I have license to do so just because he broke in -- which is a critical legal point to be aware of. Because the law in many (not all) places requires one to retreat from potential harm, if possible, rather than using deadly force. So if one shoots an intruder, even in one's own home, and it is found that the shooter was able to retreat (out a nearby back door, for example) but chose to use deadly force, not only could the shooter be criminally charged, an intruder who survived the shooting could sue for damages in civil court.
So getting back to common sense, if someone is breaking into your home and you hear it happening, get your weapon and position yourself so there is no question about retreating if you decide to shoot the intruder.
What I mean by decide is it is entirely possible the intruder, rather than some menacing hulk, will be some pathetic looking wretch, quite possibly a desperate junkie, who falls to his knees in tearful terror when he sees you aiming your weapon at him. In this event there are two things to consider: First, if you shoot this sorrowful creature, and if you have a normal conscience, you will regret it in the future. Last, you will make a bloody mess all over your carpet and possibly a hole in your wall. As it is, if you don't shoot him all he will do is piss, which is easy to clean up. So the best and, later, the simplest thing to do is order your cowering intruder to lie face down, arms entended, and call 911 to come and remove him.
But if the intruder is in any real way menacing, or does not respond to your commands to lie down, or if you're somewhat psycho, or if you're really pissed off and you just want to shoot him, aim for the belly and defend yourself against his verbal threat to kill you and his movement toward you. Just be sure you're not standing near an unimpeded means of retreat.
And, of course, your story is your life was threatened and you had no choice.