Do the touristy things, but prioritize
Like history? Les Invalides will teach you about the French military, the Pantheon mausoleum holds Voltaire, Rousseau, Victor Hugo, Émile Zola, and Marie Curie, while Jim Morrison and Oscar Wilde’s graves are in Père Lachaise Cemetery. Prefer art? Skip everything we just said and head to impressionist Musee d’Orsay or the contemporary Centre Pompidou instead. Don’t try to do everything.
Don’t go to the top of the Eiffel Tower
Similar to the Empire State Building in NYC, going to the top of the tower is overpriced and not as worth it as you think it will be. See the city from up high from the top of the Tour Montparnasse and actually have the Eiffel Tower in your view, or head to Montmartre for a sweeping, totally-free skyline.
Visit Versailles... if you have time
If you’re a history buff knock yourself out, but it’s expensive and the line to get into the palace is absurdly long. The better option is to wander the grounds for free on a sunny day.
Budget a whole day to get lost in the Louvre
See Venus and Mona, of course, but do not leave without walking through the lavish Napoleon III Apartments. The place is enormous -- wear comfortable shoes.
See Monet’s Water Lilies, then picnic in the Tuileries Garden
The tiny Musée de l'Orangerie in the southwest corner of the park is the permanent home for a handful of works by Picasso, Chaim Soutine, Modigliani, Matisse, and, the pièce de résistance, eight giant panels of Monet’s Water Lilies. It won’t take you more than an hour or two to see everything so pair the visit with lunch in the garden.
Notre Dame is obviously impressive and worth seeing (from the outside at minimum), as is Sacré-Coeur in Montmartre. But the real sleeper hit is Sainte-Chapelle on Île de la Cité. The Gothic architecture and stained-glass windows of its interior are stunning, particularly if the sun's out. Which is only from May-September, basically.
The city’s practicing artists aren’t limited to portrait-painting con men in Montmartre.
Bateaux-Mouches is cliche, but undoubtedly a great way to see the city.
Get off the beaten path
You will not be disappointed by the rolling hills of Parc des Buttes-Chaumont in the northeast.
Shop in le Marais in the 3rd and 4th arrondissements
It’s kind of the SoHo of Paris with hip, artsy fashion types and the boutiques to match. Definitely take a coffee break and people-watch at an outdoor cafe.