Our local TV station went out and talked with 86 burglars and asked them what they look for when they broke into homes. The couple of take-away points that they said really deters burglars are:
Leave the tv or radio on.
Loud barking dogs.
Leave a vehicle in the driveway.
Make the front and back doors visible, not hidden with bushes.
Lock all doors and windows.
Lock the front porch if you have one.
The article is worth the read:
Kare 11- We asked 86 burglars how they broke into homes