Paris is always a good idea. - Audrey Hepburn
Oh Paris! Each time I go to Paris, I fall in love with it a little more. I also realize just how big Paris is! It's a good thing, because not only does that mean there's more to explore. It means that you can easily walk off your pastries, cheese, and wine.
Total walking: 6 miles / 9.7 km / 2 hours
(This estimate doesn't not include walking inside the Musee d'Orsay or shopping in the trip)
(A) No Paris itinerary should start without a recommendation to a Parisian bakery. French pastry is 25% of the reason anyone visits Paris in the first place (note: estimation noted here has not been properly tested). Des Gateaux et du Pain is a bakery you must try. They have a large selection of unique breads and pastries (e.g., croissants). If you're really feeling the vacation mood, they also bring out their sweet pastries and cakes in the morning as well - many of which are made with seasonal fruits. Last time we went, I had a strawberry tart for breakfast. I swear, it had about a million tiny wild strawberries beautifully arranged on there.
(B) Musee d'Orsay is one of the world's most visited museums. The permanent collection spans four main levels with a terrace exhibition space, and the collection is presented chronologically. "The museum holds mainly French art dating from 1848 to 1914, including paintings, sculptures, furniture, and photography. It houses the largest collection of Impressionist and post-Impressionist masterpieces in the world, by painters including Monet, Magnet, Degas, Renoir, Cézanne, Seurat, Sisley, Gauguin, and Van Gogh." Given how expansive this museum is, make sure you plan enough time for your visit and adjust the rest of your day's itinerary accordingly!
(C) If you're going to cross the river, you might as well cross it using one of the most famous bridges in the world - Pont Alexandre III. "The construction of the bridge is a marvel of 19th century engineering, consisting of a 6 metres (20 ft) high single span steel arch." Four gilt-bronze statues of Fames watch over the bridge.
(D) You probably think I'm crazy... I just told you to have dessert for breakfast, and now I'm telling you to have steak for lunch. But it's worth it! You're in Paris! The Relais de l’Entrecôte owes its reputation to its single course menu: a walnut salad followed by an extra tender sirloin steak with its famous secret sauce, and delicious home-made french fries. Incredible lunch, in a gorgeous city... and all you have to do is decide on what wine to pair with it, how much more of a vacation can it be!
(E) & (F) & (G) If you love high-end shopping... you'll love Champs-Elysees. Every single high-end designer is here (they're more likely on a side-street). People come here to spend. After you've tired yourself out from luxury shopping, swing by the Publicis Drugstore at the Arc De Triomphe end of Champs-Elysees. In the very back, you can sit down and grab a nice glass of champagne at the bar. Prices are reasonable for where it is, and the snacks are really good too (if you're still hungry after the steak lunch)!
(H) There are way too many good dinner spots in Paris. You probably don't even need to do any research. Look around and find a bistro (preferably slightly away from the biggest main roads) that has lots of people, go in and order whatever the waiter tells you to order. But if you really want to treat yourself... I'd recommend making a reservation at Restaurant David Toutain (a two Michelin starred restaurant).