This is for another friend, here are my pointers:
1. Find a very good food street/corner and take many of your meals there. I’ve used Rue Daguerre and around Rue des Arts (Left Bank) for this purpose, but there are many others. Spend most of your money in the cheese shop, asking them to choose for you, but supplement with bread, fruit, and of course chocolate. This beats most restaurant meals, noting it won’t be cheap either. And yes it is worth paying $8 for a bar of chocolate there.
2. Do track down medieval Paris, most of all the cathedrals. This will bring you by other delights as well.
3. Especially on the Left Bank, Paris is one of the very best walking cities. Avoid Champs-Élysées and environs, a broad-avenued, chain store-intense corruption of what Paris ought to be. Avoid Jardin Luxembourg and the surrounding parts as well, they are urban deserts.
4. Get a peek of the major bridges over the Seine, if only by traversing them.
5. You don’t in fact have to stand in line to see the Mona Lisa. It’s a lovely painting, but at this point in human civilization it is OK to skip it. You don’t need to hear “Bohemian Rhapsody” again either. But you should go to the top of the Eiffel Tower. And in the Louvre, don’t neglect the Poussin room, the Michelangelo sculptures, or the Flemish and 17th century works.
6. The Louvre, d’Orsay, Cluny, and Branly (ethnographic) are the essential museums in town. Check out Grand Palais and Petit Palais for possible exhibits. When walking around, keep your eye out for posters (yes, posters) advertising exhibits and concerts.
7. If you want to spend forty euros for a very good but not revelatory lunch, find a “cool” area with lots of restaurants and poke your head in at their opening, at 12:30, to ask for a table. By 12:45 it is too late and you are screwed and back to your favorite cheese shop. By the way, I don’t think Paris is the best city in which to spend $200 on a meal.
8. In most of the parts of Paris you are likely to frequent, do not try to eat any Asian or “ethnic” foods. The best restaurants of those kinds are in north Paris, on the way to the airport, but no one visits there. Couscous in Paris is boring.
9. Belleville is the gentrifying Brooklyn of Paris, with relatively few tourists, if that is what you are looking for. Avoid Montmartre. For practical reasons, I’ve spent a lot of my Paris time near Unesco, in a neighborhood that is a bit sterile but very beautiful and it gives you a decent sense of well-to-do residential Paris life. Develop your mini-Paris residential life somewhere, and make your time there more than just a tourist visit. The site I should not enjoy but do is Le Dôme des Invalides, also the tomb of Napoleon.
10. The essential Paris movies are lots of Godard (Breathless, Band of Outsiders, others), Jules and Jim, and Triplets of Belleville. Agnes Varda’s Cléo from 5 to 7 for those with an experimental bent. Eric Rohmer for something light-hearted. Amélie and Before Sunset are both rewarding, though at the margin Godard usually is what Americans are lacking.
11. Carry along Hugo and Balzac to read. Flaubert and Proust are wonderful, but they are more “interior” authors and thus you can imbibe them anywhere. Do not forget Houllebecq’s Submission. I do not love most of the well-known non-fiction books on Paris; perhaps they become corrupted through the chance of being truly popular. Do read Graham Robb’s The Discovery of France and try to dig up a useful architectural guide to the city. I’m also a big fan of Hazel Rowley’s Tete-a-Tete: Simone de Beauvoir and Jean-Paul Sartre.
12. Don’t go expecting Parisians to be rude, I have never (well, once) found that to be the case in more than six months spent in the city.
13. My overall take is this: Paris today is fairly sterile in terms of overall creativity, or for that matter business dynamism. But Parisians have perfected the art of taste along a number of notable dimensions, like nowhere else in the world. If your trip allows you to free ride upon those efforts in a meaningful way, it will go very well.