Last night I took a late trip to the store. I returned 15 minutes later and just as I was closing the door, I heard a rustle and something fall. Before I knew what happened, I had my Glock 27 in my hand and I'd crouched into a shooting position but holding the gun close to me. I also realized I'd left the back door open.
After listening for a few seconds, I started to realize that it was probably nothing. I looked around the corner, G27 in hand, and saw that a plastic-wrapped roll of large paper had just happened to fall over as I came in.
Just for the hell of it, I went ahead and "cleared" the house. I realized that I could have been killed a few times over. I didn't really have a strategy for turning on the lights and moving from room to room without casting shadows or being seen. I realized that in my house, the light switches are not always at the same height or the same distance from the door/corner.
Now of course, in a situation where someone is in your house, you should leave and call the PD if you can. However, what if you can't? What if your kids are at one end of the house and a burglar at the other? What if...?
Practice clearing your house. Practice with your spouse, and practice alone. Do it with an unloaded weapon. Learn the potential hiding spots, and learn where you can enter a room so that you are not vulnerable to side/rear attacks.
Like I said, nobody should go in their own house if there is a probability of a burglar. But you should be prepared in case you have to.