It's important to arrive at the star party to set up, settle in, and give your eyes some time to adapt to the dark before it is already too dark to see. There are always a few stragglers who arrive late, but this is usually frowned upon because those already there don't like headlights shining at them after their vision has become adapted to the dark. When you arrive after dark, you also run the risk of not finding the place at all: Many sites that are easy to find in the daytime can be nearly impossible to find at night.

If you arrive before dark you'll also have a chance to see all the telescopes being set up, which can be particularly interesting with the really large scopes some people bring. You'll find that most astronomers are quite talkative and willing to discuss their equipment and how it works, particularly if you offer to help set it up.

If you do have to arrive after dark, turn off your headlights far enough away from the viewing area so they won't disturb anyone. Drive in the rest of the way using your parking lights. When you first turn off your headlights the parking lights may seem inadequate, but if you give yourself a minute to become more adapted to the dark, you'll find that you can drive just fine.