1. Don't speak French. Ever. Period. I don't care if your nanny was a native Norman and you've practiced since you were five. To a Parisian, you'll still be pronouncing it wrong. Besides, the French don't expect us to speak their language, and they are a people with a small capacity for thought. Best not to surprise them. Communicate like any American, by gradually raising the level of your voice and pointing at things until they understand perfectly.
2. Don't laugh at their history. If you go up the Arc d'Triumph, you'll find a museum at the top that lists all the wars France has single-handedly won. They include World War I and World War II. Sure, you and I know better, but the French still think the world looks up to them and this whole "U.S." thing is some kind of fad. It's a short-man complex on a national scale, but what else did you expect from the people who brought you Napoleon?
3. Don't eat the snails. I refuse to be held responsible for the consequences.
4. Do go to the museums. Paris has some beautiful pieces of art, mostly from other countries. Yes, go to the Louvre, so you can stare at the Mona Lisa, a portrait whose actual size is slightly smaller than a postage stamp. Despite the fact that there are thousands of pieces of art in the Louvre's collection, ¾ of the people in the museum at any given time can be found in front of this one painting. Some other pieces I recommend instead: "The Wedding Feast at Cana," by Paob Caliori, which is in the same room and a hundred times bigger; "The Raft of the Medusa," by Theodore Gericault; "Eros and Psyche," by Antonio Canova, a moving sculpture; and "Gallery of Views of Ancient Rome," by Giovanni Pannini, my personal favorite.
5. Another note on museums. If you're going to more than one, save the Louvre for last. The sheer splendor of the building itself makes the other museums look small. It's like going to Disneyworld and then the local county fair.
6. Do go visit the Hard Rock Café, or some other typically American hang-out. I'm all for learning about another culture, but after three days of hearing nothing but French, I was overjoyed to hear, "What's up, guys. Y'wanna cheeseburger or something?"
7. Last of all, have fun. True, Paris isn't like your hometown. But then again, if it was, you wouldn't have flown across the Atlantic to see it. If your hometown's like mine, once you've seen the cannon in the park there's not much else to do.