No Trespassing Laws

No trespassing laws very by state.  Know the laws that apply to the area you are plannig on flying before you go flying.  Some states give you a free pass the first time, but once you are asked/told to leave you could be cited or arrested.  Some states consider a posted "No Trespassing" sign as that first warning, so, look for signs, then look up the law that is referenced on the sign.  If the sign just says "No Trespassing" and does not reference the state or local law/ordinance that gives the property owner the right to post the sign, it may not be a legally posted sign.  Private citizens who post a "No Trespassing" sign (on public property) because they don't want you to use a public access path leading to "their private beach" may actually be breaking the law by trying to deny the public free use of the public property.

Here are some examples of state trespassing laws.  If you don't see your state listed, go to Google and search for "trespassing laws in <my state>".