If you are unfamiliar with a location, try to arrive before sunset as bright headlights can ruin dark adapted vision in a fraction of a second. There is nothing that bothers observers more than headlights after dark. You don't even want to know what astrophotographers think of headlights. Do your best to leave with your headlights off as well. Someone will gladly guide you out of the site with a red flashlight if it means that you will leave the headlights off.
Flashlights are just as bad as headlights.
If you need light for any reason, try to make it red light. Many astronomy stores sell small LED flashlights which only emit red light. Or place some red plastic over your regular flashlight lens. It makes a world of difference. Astronomers are usually a friendly bunch but always be polite and never touch another person's equipment without permission.