Do not lean on walls or climb on roofs. They can collapse causing injury to you and extensive damage to the ruin. If there is an established path leading to ruins, be sure to stay on it to avoid crushing the midden and any artifacts, either hidden or on the surface. Walk carefully around the slopes that support these structures. The passage of too many feet can undermine the foundation of rock walls, leading to their eventual collapse.
Ruins are an interesting highlight of a hike, but are inappropriate places to make camp.
After observing an archaeological site, move on before having meals. Food crumbs and garbage may attract rodents that could then nest in the site. Leave all artifacts where you find them. Some people will take one or two potsherds, thinking that they will not be missed. Yet it is the cumulative effects of this practice that leads to fewer signs of the Anasazi culture each year.