We get the same problem on our property. Not cig butts though(not that I know of). We have caught a couple people, one person on numerous occasions. Its not a fun deal. I would say 99% of the time, they know they are on private property, especially with oodles of posters up. Those ones are just plain ignorant.

you have to make sure they know you are serious and will take the proper steps if neccesary.

Our property is 600 acres, its hard to catch all of them, but we do occasionally and have taken other steps to ensure they don' t show up again.