how to mark your camp spot as taken?


New Member
we will be trying RV (C class) for the first time next week and we plan to stay in free campsites for couple of days (BLM and such) and i was wondering how do you mark your camp spot as "occupied" if we will leave for couple of hours to hike or get food or whatever but still want to come back for another night at that spot? are there any camping unwritten rules we need to know about? (also so we wont grab someone elses spot by mistake)