Lots depends on the campground. In a monitored campground (private or organized government), I just leave the utility connections, what ever is on the table, chairs, etc, as each spot is supervised by the staff. In a non-monitored campground, I gauge the surroundings and may leave stuff or may pack most of it up; it all depends on the feel of the area and occupants. I do have a government issued "Do Not Enter" sign I use at federal, state, county or municipal campground and have never had anyone try and sneak into the spot.
If anywhere but a quality RV campground, it comes down to your observation of the campgrounds and users. The regular method I see that seems to work the best is cones with a bight colored rope between them across the entrance. Not sure why that works so well, but it appears too.
