The best way to keep feral cats off of your property is to just not put out food or water. With no food or water, feral cats will eventually move on. Personally though, I wouldn't be able to do that. Cats are living beings, and I believe that people need to be responsible in getting cats spayed or neutered, to try to keep the pet population down. If there are cats on my property, I'll put out food and water for them. If I can, I'll trap them, and get them in to get fixed, and then release them again. In most instances, there are non-profit organizations who will help in getting cats fixed. We're all in this together, so I believe it's good to work together to put a stop to the over population of stray and feral cats. In the same respect, I do understand that there has to be a limit as to what we can do for these ferals. So it's kind of a catch 22. The important thing is, if you can't help these ferals, then the best thing to do is just not put out food and water for them.