Oh boy, I'm gonna catch all kinds of flak for this one...
About 5 years ago, my extremely loyal, territorial Heinz 57 pound puppy woke me up in the middle of the night by pawing at my side of the bed. At first I thought he wanted out to go potty, but when I started toward the back door he looked at me kind of strangely and headed toward the attached garage door in the kitchen. Knowing something wasn't right, I returned to the bedroom for my Mossberg 590. I went to the kitchen door to the garage, stopped and listened, and sure enough someone was fiddling with the outside door knob on the other side of the garage trying to break in. I stepped back and slightly away from the door and racked the slide on the shotgun as loudly and distinctly as I could.
Presto! The noise of the garbage can outside being knocked over as someone beat a hasty retreat was my reward.
A couple of points here: I didn't have to worry about clearing the interior of my house since my dog had already done that for me. Yeah, yeah, I know all the stuff about racking the slide on a 12 gauge not killing anybody. Spare me. That's the idea, that you have an opportunity NOT to shoot somebody if you so choose.
After a minute or so, I turned on the outside lights, let my dog out and together we cleared the yard, me with flashlight and shotgun in hand. I've got my lights positioned so I have convenient pools of shadow from which to observe the yard and move to the next position. The garage door had some scrapes in the paint from what looked like a screwdriver, so it was probably a kid or a rank amateur.
Bottom line: dogs are your best friend when it comes to home security. They'll check out the house for you without ever thinking about the risk to themselves. Firepower does you no good if you never wake up to use it. There are lots of other good suggestions here, but dogs and motion detectors are kind of mutually exclusive unless the dog is gonna stay in the bedroom with you. Stay safe, get training, and if your situation allows it I'd consider getting a canine companion, the more territorial the better.