Just use common sense for God's sake. It's not that big of a deal, if you are in a fairly urban area like anything in the northeast part of the country, forget about it, you are likely to get arrested. In the midwest or the south, if you are several miles down a road and see no sign of human habitation, try to get a few hundred feet off the road and you are completely fine. Out west, so much area is public land, if you are not in someone's yard you are usually OK. Just follow and obey no trespassing signs, if someone doesn't want you there they usually let you know it. Tread lightly, it goes a long way toward helping your cause here. No fires, no music, move on at dawn. If no one knows you were there, it's not a problem, now is it?