I tend to be a bit heavy on locks. For example, this is a suggestion on locking a bike in Austin:
It is true locks keep an honest person honest, but I use them in the vein of "outrunning the bear" (where one doesn't have to be the fastest, just quicker than the slowest guy in the group.) I don't try to have the most secure rig... just more obviously secure than the other people, so the thieves go elsewhere.
The "STOLEN" sign is a definite idea. I have seen that idea elaborated on in a storage yard. One person had, on their stored trailer, an extremely vulgar sign where the license plate is normally located... obscene enough that it would get people calling the local popo to report the vehicle.
Of course, there are a ton of Kickstarter projects for small trackers that use both a tiny 3G radio coupled with a GPS and a small battery. Toss 2-3 on a vehicle, so a thief sees one, gets rid of it, and thinks the job is done.
As for me, I lock my vehicle down, and if someone does cut my X-chocks off, that is what insurance is for.