4 days in Paris

I found it helpful to start with the list of free entries on the Paris Museum Pass and plot/save them on Google maps. When you click on something in Google maps, Cluny for example, a side bar shows the times they're open. When you save it, a star will stay on the map and you can see how things relate to each other. I think this can help you start developing a plan for what to see and when to see it.

Keep in mind the hours this week will change slightly based on the time of year. They're open longest in the summer and shortest in the winter months.

My suggestions:

Walk Ile de la Cite and St. Louis island. Go inside Notre Dame and St. Chappelle. Walk banks of the Seine.
Visit Eiffel Tower, go up to at least 2nd level if you can (with advance ticket). If not, view from ground, but be sure to see the twinkling lights at night, on each hour after sunset. You can see this from a nighttime Seine cruise if you time it right.

D'Orsay and Louvre museums. If you go to the Louvre, before or after, walk down through the Tuilleries garden towards Place de Concorde. Great strolling place.
Take metro or taxi to Arche de Triomphe, no need to spend time walking down the Champs Elysee.
Since you are in the St. Germain area, I hope you have time to sit at an outside table at either cafe Deux Magots or Cafe Flore (though there are many others) -- and sip a coffee or glass of wine. Pricey, but wonderful people watching and being part of the scene. I especially like Deux Magots since the tables look out on St. Germain des Pres - you should go inside this old church too.
Luxemburg Garden is a lovely place to stroll --always beautiful flowers.
Of course don't miss trying the food --- stop often at bakeries and cafes.

Thanks so very much!!

Tuesday
Sacre Coeur & Montmartre
Eiffel Tower
Seine River Cruise

Wednesday
St Chapelle (amazing stained glass) ...opens 9.30am (summer)
Conciergerie (where Marie Antoinette imprisoned)
Arc de Triomphe (must see view from top)
Tuileries Gardens
Orangerie (Monet's waterlilies)
Louvre ...closes 9.45pm Wed, Fri

Thursday
Musee Cluny (museum of the middle ages) ...opens 9.15am
Pantheon (dedicated to the greats of France)
Luxembourg Gardens
Musee Rodin (famous bronzes in beautiful gardens)
Invalides (Napoleons tomb)
Musee d'Orsay (Impressionism) ...closes 9.45pm Thu

Friday
Tours de Notre Dame (walk up the towers and get close to the gargoyles) ...opens 10am
Notre Dame
Place des Vosges
Musee Picasso (recently renovated)
Pompidou Centre (modern art collection) ...closes 9pm

Thank you all so much. And David- thank you so very much for breaking it down like that. I'm going to follow that schedule. It's exciting and nervous traveling alone for the first time in Europe. I appreciate you all sharing your thoughts and experiences.

No problem, you're welcome.
Paris Museum Pass is a good idea for you - 2 days, or even 4. http://en.parismuseumpass.com/
You didn't mention your arrival or departure times, so don't try and cram too much in.
The above suggestions are grouped by location to make it easy for you.
Don't try and do everything, but take advantage of the museum late closings on Wed and Thu.
If you plan the Towers of Notre Dame the get there an hour before opening to queue.
Eiffel Tower is best booked ahead if planning an ascent.
Vedettes du Pont Neuf is a good choice for river cruise ... http://vedettesdupontneuf.com/home/
Paris is wonderful. Enjoy.

David's suggestions are great! I'd also suggest adding a visit to at least one market or market street. Nearby Rue Mouffetard (in Latin Quarter) isn't far from St. Germain, or marche Monge on rue Monge (Wed & Fri) and marche Maubert (Tues & Thur) -- the markets open at 7, if you're an early-morning person. There are many other wonderful ones throughout the city, but these are close to you. For great (organic) crepes, just off Blvd. SG, I like Little Breizh – 11 rue de gregoire de tours. Loads of great bakeries in the 6th - you'll be in heaven.

Thanks very much! I am going to follow your iternerary and will get that pass!!! I'm arriving Tuesday early morning and leaving Friday night so this should be perfect :-)

On Wednesday, after Conciergerie, take metro line 1 to Arc de Triomphe (Etoile) and then to return to Place de la Concorde.
Walk ... Place de la Concorde >> Madeleine >> Opera >> Place Vendome >> Tuileries >> Orangerie.
Then head to the Louvre.

Thank you David!!! Do you think on Tuesday I could also fit the Musee Rodin and
Musee d'Orsay since I believe they're open on a Tuesday and I'm arriving that day at 10am? I'm going to be well rested since at that point I'll just be taking the eurostar in from London....

At 40 yrs old and in pretty good shape, we found a heavy-museum schedule grueling. It's not just getting there, it's all the walking and standing once you get inside. We started to just pick the few things we really wanted to see and spent more time taking breaks at cafes. Stopping every couple of hours, getting a drink and small snack, getting to use les toilettes, made for lovely long relaxing days.

The river cruises are a great idea.

Hot tip: don't wear open toed shoes to the Tower, Louvre, l'orangerie or Tuilleries. Not paved, it's mix of gritty sand and tiny pebbles that get in your shoes, tres uncomfortable.

We did the market streets on Tuesday, and took a dinner cruise that night.

Every bathroom is an adventure. Many are gender-neutral and you may find yourself in a stall with a man peeing in a urinal 2 feet away.

You can't throw a stick in Paris without hitting awesome architecture or street views or great food. Just wander and let Paris lead the way.

We stayed next the Louvre but after visiting all of the neighborhoods, we will stay in St. Germain next time. You'll love it.