(This thread prob fits better in "Rural Living", not that it matters much)
I didn't see where OP said what state he's in, but hopefully he/ you can find something like this for your state, but here's ours for FL:
588.09 Legally enclosed land; fenced and posted.
(1) Land shall be legally enclosed land, or posted land, when enclosed by a legal fence, and when there shall be placed along the boundary of said land in the manner herein provided posted notices to the public; provided that it shall not be necessary to erect any fence along any portion of the boundaries of the land formed by any ocean, gulf, bay, river, creek, or lake.
(2) The fences, enclosures, and the posted notices, when erected, placed, and maintained as herein required shall be notice to the public that the land enclosed thereby is private property upon which unauthorized entry for any purpose is prohibited and shall constitute a warning to unauthorized persons to remain off of or to depart from said land.
588.10 Posted notices; requirement.
Posted notices to the public as required by s. 588.09 shall be signs upon which there shall appear prominently, in letters of not less than 2 inches in height, the word "posted", and in addition thereto there shall appear the name of the owner, lessee, or occupant of said land. Said posted notices shall be placed along, on, or close within the boundaries of any legally enclosed or posted land in a manner and in such position as to be clearly noticeable from the outside of the enclosure, and said notices shall be placed not farther than 500 feet apart along, and at each corner, of the boundaries of the land, and also at each gateway or opening of the fence enclosing the same. Said notices shall be placed along all boundaries formed by the waters mentioned herein on trees or posts close to the banks of said waters in position so as they may be noticeable to persons approaching the boundary formed by said waters.
FE111/FE111: Handbook of Florida Fence and Property Law: Visitors and Responsibilities to Visitors <-- There are some very interesting examples here
What notice must be provided to a trespasser?
As previously mentioned, under Florida Statutes section 588.10, a property owner must provide proper notice to all parties that may enter the property. All gates, fence corners, and all boundaries that lay along waterways must have posted notices of proper size and composition. The postings can be no more than 500 feet apart. If no notice of trespassing is posted on a piece of property and the party cannot know who owns the land, the party may not be able to be assumed to be a trespasser. This may change the party's status in liability for damages for harm that may befall that individual. Certain facilities require different wording in the posted notices, and a different penalty for the person caught trespassing.
To what extent am I, the property owner, responsible for trespassers?
The property owner's duty to such persons is to not intentionally injure the trespasser. However, if the property owner knows or has reason to know of trespassers on the land, the property owner must warn the trespasser of dangerous conditions that are not open or obvious to the trespasser (Dyals v. Hodges, 659 So.2d 482 [Fla. 1st DCA 1995]; 41 Florida Jurisprudence 2d Premises Liability section 61). Although there are few cases dealing with liability for the conduct of trespassers and others acting without the possessor's knowledge or consent, it is clear that there is no liability until the possessor knows or should know of the likelihood of trespassers and has had a reasonable opportunity to exercise the proper care to prevent injury to others (Fisel v. Wynns, 650 So.2d 46 at 49 [Fla. 1994]).
For example, if P sneaks into the property owner's pool without the property owner's knowledge and then drowns, the property owner is not liable because the owner is only responsible for not intentionally harming the trespasser (Pedone v. Fontainebleau Corp., 322 So.2d 79 [Fla. 1975]).
As stated in the above paragraph, the property owner does have the responsibility of warning the trespasser of known dangers not ordinarily visible if the owner knows or has reason to know that the trespasser is present on his property. This area has been the subject of much controversy and many court cases.
... and more ...