At Farley Hill the ambience is not so dark that one needs to be obsessive about lights but looking directly at lights is to be avoided. Keep all lights pointing down or away from others when possible. Red is the best colour for preserving your night vision and any torch can be covered with red cellophane. Babybel wrapper is fine!
Computer screens and camera menus can be quite bright. Face towards your companions when using such equipment, so they only see your face glowing. A lot of software for use outside at night has a red mode. I find it impossible to use, too dim and hard for my eyes to focus. Don’t bother with it if that is the case.
If you arrive in the dark and others are already observing we like to know who is turning up. Say “hallo” at least or “it’s only me”. Despite what you might expect, astronomy can be a social activity! Anoraks are for wearing.