Some friends of mine had traveled to the ACM programming contest many years ago. After the contest, they decided to get dinner. Despite wearing T-shirts and jeans, they decided to try the 4 star restaurant that was nearby. The maitre d’ very politely apologized, but said that he couldn’t seat them as they didn’t meet the dress code.

Then they tried the 5 star restaurant in the same area and were promptly seated. They related to the maitre d’ what had happened. He responded “That’s the difference with a 5 star restaurant. We don’t have to try to get our class from our customers.”

At a very high-end restaurant, there are no rookie mistakes. The staff is there to make your time with them as enjoyable as possible. Some of the other answers describe some things that you might decide to do in order to help with that goal, but ultimately you know better than anyone else what will make the meal enjoyable for you. So relax, ask whatever questions you have, don’t worry about what others think (since they are probably thinking about themselves), and celebrate that you’re able to have this nice experience. (Of course, that’s good advice for most experiences in life.)