BLM & USFS, many State lands are open to dispersed camping. Many are not. Inquire from the dept. for maps, before you go. the USFS calls theirs MVUM ( motor vehicle use maps ) that show where and when you can camp on or use forest service land.
BLM & State lands have their own rules, of dispersed camping locations and ' marking your site'. while away for the day is accepted with personal effects
14 day stay limits are the normal, with a move of 25 miles to the next site.
I have seen this rule broken in Az. BLM, rigs a month or more in the same spot. Here in the Black Hills NF , it is enforced. A ranger will make you move.
Off Road Vehicle use on the land seems to be a concern, with wild land fire major. The areas Ive seen off limits to dispersed camping are areas with tall grass, dense forest, remote for emergency fire service.
Get out and enjoy your lands. Be respectful, do no harm. Any unnatural marker you are away for the day should do.