Trailer security

I'm considering a new trailer purchase Other than keeping your trailer out of sight or a locked fence, what are ya'll doing to keep it safe. I have reviewed several locks, just wondering what you have done. Also, interested in real stories of thieves that were thwarted by your efforts Craig
I just sold my aluminum open car hauler. I had room to store it on my property. When not in use I had a lock that fit up into the ball hitch. And I stored it with the hitch in towards a dead end - fence. I have a dolly that hooks to my riding tractor that I used to drive it out. During the off season-winter months, I took all for tires/wheels off and had the trailer up on blocks, stored the tires inside out of the weather.
My trailer also had the serial number sticker in two places. One up by the tongue where one would expect it and a second duplicate up inside a channel visible only with a flashlight and mirror.
The salesman explained that if the trailer did get stole and recovered, but the thief had obscured the normal vin tag, the duplicate hidden tag could be used to prove ownership. I though that was a good idea.