My first line of defense is frequent gunfire from my range near the house. People around me have experienced some petty theft throughout the years, but so far not my place, and I'm the only one who shoots regularly. Everyone who lives around here knows I have guns and know how to use them.
Failing that, there's a 12-gauge pump shotgun near every outside door of the house, loaded with Super X 00-buckshot. I can't think of any more universal show of force than a pump 12-gauge...everyone gets it, there is no language barrier when that gaping tube is pointed at your face and the dude (or dudette) wielding it means business. Handguns hidden in plain sight in each room of the house, and plenty of other things I won't go into. Main thing is my wife or I can have a weapon in hand in five seconds from any point in the home.
It might seem paranoid, but we live near a very trashy community and have had more than a few unwelcome trespassers over the years. Well armed and with a plan, there's little need for paranoia.