We have multiple layers of defense starting with 4 outside lights front, side and back, a street light in front of our house and security doors front and back. We have bars on three of our windows that the highest risk area on the side and back of the house and the rest of the house has ACE security glass that they claim is bomb resistant, not just bullet resistant. All windows have screw on individual locks. These defenses are for the smash and grab creeps.
We have a full alarm system with inside motion detectors that we put on every night when we do not have kids or friends over. We have a double door to our bed room with four locks on it backed up by the 2X6 plank. All of these fortifications are designed to slow the creeps down if they get through the first layer of defense to give me the time to get to my assortment of weapons and ammo readily available at all times.
When we enter our house, we always listen for the alarm to beep. If it doesn't, then I check the entire house from top to bottom before relaxing my vigilance.
Lastly, my wife and I watch ID, Dateline and other crime based TV shows of real life events just to stay paranoid enough to keep up the watchfulness and preparation. I have a new condo up north that I will have to "zombie" proof as well but won't be able to use bars on any of the windows because of CCRs. But up there, I can at least carry my weapons with my CCW permit so that puts me one step ahead of any bad guys since that goes with me everywhere.
It is more a state of mind than the actually barriers that is the most important in securing home defense options.