Signs (depending on how big your place is), locks on the gates, liability insurance are all good ideas.
Some people may still disregard your private property rights, and just like our horses, get themselves into some unbelievable mess.
Some in our state (WY) have found that a good old countersuit against the nimrod who tresspasses and does something stupid is a really good deterent to frivolous insurance claims and lawsuits. We can sue tresspassers for pounds run off our beef, amount of forage ruined, diverted water when some idgit sets up camp by a tank (well) or spring and prevents livestock from access. Game and Fish can join in and sue for harassment of wildlife and preventing wildlife from accessing water.
Fortunately for me, WY courts strongly support private property rights and the burden is on every individual to know where they are. I don't have to draw anyone a picture, so to speak.