Notre Dame - point zero of Paris, the perfect starting point
City bus tour, get your bearings, see the sights by day.
Louvre - see the Mona Lisa and pick a few other highlights
Eiffel Tower - go up but the best part of the skyline is missing. twilight is great.
Seine Boat Tour - see the city at night, and return to Eiffel to see the sparkles on the hour starting at 10 pm.
Arc de Triomphe - please don't cross the street, use the tunnels
Champs-Elysees - shop, eat, drink
L'Orangerie - see Monet's famous waterlillies here and no where else.
Musee d'Orsay - get your fill of the Impressionists here - start on the top floor
St. Chapelle - small beautiful church
Picnic on the Seine - baguettes, some Brie, a few bottles of wine and a blanket
Le Marais - see Place des Vosges, maybe the free Carnavalet museum, cool shops
Pere Lachaise - say your regards to Proust, Sarah Bernhardt and the Lizard King
Montmartre - twisty hilly streets, famous strip clubs, artist hangouts
Sacre Couer - wedding cake church at the top of Montmartre
Optional Day Four
Versailles - buy your tickets online AND go early
Giverny - Monet's country home