Here's the last installment of my tips for beginning star-party goers.
Never move someone's telescope without permission. If the object you're observing seems to be drifting out of the field of view, briefly mention this to the telescope's owner. He or she will more than likely show you how to adjust for that, either manually with slow-motion controls or with an electronic hand paddle. Sometimes, especially if the scope's balance isn't the best, the owner will trade places with you briefly to re-center the object.
Check the rules before you smoke. There may be a fire hazard. Note the direction the breeze is blowing and be mindful of others who do not appreciate secondhand smoke.
Beware the words "imaging" and "astrophotography." People involved in such endeavors are likely (as a general rule) to be less sociable, at least while performing those tasks. Use no lights in the area, don't walk in front of their telescope or even too closely, and only engage in the amount of conversation they are comfortable with. Some amateurs who live in harsher climates look at the generally clearer, darker, drier sites that star parties provide as a way to acquire new images, rather than as a nighttime social event.
Arrive before dark. There are two reasons for this: 1) After telescopes have been set up, lights from vehicles are frowned upon - strongly! 2) You may literally not be able to find the location in the dark. Star parties are generally held at remote sites, making them nearly impossible to find after sunset (even with directions). If you have any doubt about your ability to get there, a good idea is to visit the location during the daytime.
If you're not staying all night, let other star-party attendees know you're planning to leave. Somebody may be in the middle of imaging. For the cost of a few minutes time, you can avoid making an enemy. Use double the care with vehicle lights when leaving as you did when arriving, because everyone's eyes will be dark-adapted.
Finally, and most importantly, be courteous! The people you meet are not being paid, and they're especially not being paid to serve you. Most are either members of an astronomy club or their spouses. The rest of the attendees will be visitors just like you.