The most common local BLM regulation is that you can't spend more than 14 continuous days in one location. After that, you have to move a certain distance away before you can legally camp again. After a certain length of time (typically 14-76 days), you can legally return to the original campsite and camp again. Thus, by hopscotching around like this, you can live perpetually on public land without paying rent or asking anyone's permission.
How does anyone know you have spent more than 14 days in one location? They don't, unless you do something to tell them. BLM rangers, who are responsible for enforcing the 14-day rule, are usually spread thinner than soap film over a vast territory. You'll be lucky if you see one in a lifetime, let alone twice within a one-month period. Like most law enforcement, they don't usually go out looking for illegal campers. Instead, they wait for complaints to come to them. If you choose a discreet camping spot, leave no visible signs of your presence and don't give anyone any reason to complain, all this land is basically yours.
The only drawback to public land is that you usually need a vehicle to reach it, as it tends to be located away from urban areas and public transportation.
How do you identify public land? First, it is only in the Western States (as shown above). Secondly, there is a notable lack of No Trespassing signs and border-marking fences. If, for example, you are driving on a local highway in Nevada or the California desert, away from any town, and there is no fence along the road, the land is probably public. The best record of whether a certain area is public is a local land-use map, available from the BLM.
Whenever I am traveling in the West, I liberally interpret my right to camp. Once I encounter open, inhabited land that appears to be public, I simply camp there, preferably out of view of the road. I hold it the responsibility of the government or landowner to tell me I can't camp there. And if my presence is secret (primarily for safety reasons), they are never going to know I'm there, so they won't have the chance to tell me anything.
Why doesn't everyone live on public land? It's the same problem of real estate everywhere: location, location, location. Public land is fine if you want to get away from it all, but sooner or later you are going to want to interact with your fellow man (and the services he provides). If you want to do this on a regular basis without an hours-long commute, it will probably require sleeping in an urban area where public land is rare. That's when you have to get stealthy and marginally criminal of you want to sleep for free.
LinksHere are some general BLM camping regulations (in this case for the Mojave Desert near Barstow) as published on an official website:
Except for "special areas" with specific camping regulations, visitors are welcome to camp anywhere on BLM managed land.Note that it costs $6 to camp in a campground but nothing just outside it.
And here are some exact local regulations, as published in the Federal Register. Although the exact regulations vary from place to place, the 14-day limit seems pretty universal. The only thing that varies is how far away you have to go when the 14 days are over and how long you have to wait before returning. Again, if you keep a low profile and never develop what appears to be a permanent encampment, the 14-day limit is pretty meaningless.