Never touch any glass optical surface. Avoid loud and boisterous behaviour. Star-gazing is a quiet, peaceful activity. Drive very slowly so as to avoid kicking up dust. Be especially careful of wires on the ground.
Some scopes require power and some folks use their car's battery.
If your scope requires power try to make the wires as safe as possible. Don't set up too close to another observer. If you're a visitor or a newbie, try not to monopolize another person's time. The astronomers are there to enjoy the sky, not to give lessons. If you bring your pet make sure it is firmly under control.