Since I used to get money and food by stealing, when I was growing up...
Believe me.
Motion detector lights work. It has to be really appealing to make me keep setting off the light to see if anyone checks on it, or figure out the detection limits.
Fences are useless. I'll go through any fence in seconds. I'm out there (well, not anymore) with bad intentions, I have tools.
Dogs are 100% effective. Size doesn't matter. Post SHTF, maybe people shoot dogs to get stuff, but not now. Dog barks, I leave. I see a dog, I leave because it's gonna bark.
If I set off an alarm, I'm going to back off and see what happens. Time the police response, if any. See who comes out. Take note of numbers of people, versus number of vehicles. Probably something good in there, worth the effort and wait.
Don't leave guns in cars. I've never taken one, but I've found a few.
If a safe can be picked up, consider it gone. If you have a heavy one, and I have time, I'm going to look for a wagon or hand cart. Seriously.
Consider appeasement, but don't count on everyone being cool. We had a guy that left his garage and car unlocked, and once a week we would get a few roaches from under his car floor mat. Did it all summer. Then someone told someone stupid and he broke into the house to steal it all, and got a gun in his face for his troubles. Post SHTF if I'm out stealing food, I would take few cans at the end of the lane and be grateful, but there are some bad, stupid people out there.