You can easily walk from Invalides to the Rodin Museum.

Metro stops within the inner arrondisments are closer than you think from the map. I still remember from many years ago getting off the Metro with my wife after two changes to get really close to our goal. We saw the original Metro stop a short walk away! This eventually led to our rules: If it's only one stop away, walk. And: Most of the time, changing trains is equivalent to walking one stop.

I see that you are actually talking about taking the RER C which is different from the metro even if it uses the same tickets.

If you use

http://fr.mappy.com

enter your destination and choose the options "Transports en commun" and "Plan", you will get a map showing how the various public transport options relate to the street map. So, for instance, the Musee Nissim Camondo is about equidistant from the Monceau and Villiers stations, but a bit further from Miromesnil, whereas the Jacquemart Andre is about halfway between Miromesnil and the Nissim Camondo. All are within walking distance of each other.

Enter Google - Maps, put there your location and destinations; you can select by walking, or by public transport and get indications and a map.
I tried fro you - from the hotel till Opera ; it is 1.5 mile

Some basic things to know:
1. each metro line (and RER) have "direction" endpoints to help send you to the correct platform for the direction you want to travel
2. looking at a metro map, the white circles and ovals indicate intersecting metro (RER) lines where you can change / transfer to another line (in the underground, note again the 'direction' of the subsequent line you'll be taking)
3. inside each car is a graph of that metro/RER line, so you can compare stop names as you pass through them to the graph to ensure you are going in the right direction
4. if you make a mistake, get off at the next stop, go around to the other side of the platform and go back to the station where you went 'wrong'. It isn't traumatic, just slightly inconvenient.
5. keep your used ticket until you have completely exited the system then you can toss it
6. don't set your bag down inside the metro car, especially if you are near a doorway, and don't leave a backpack or such purse on your back, behind you - move it around to your front so you can watch it
7. your feet with Thank You for interspersing metro with walking

7. your feet WILL thank you....

I would walk from your hotel to the Rodin Museum unless it's raining hard.

Another metro route would be to walk to Metro Mabilon (about the same distance as St-Michel Metro), direction Boulogne, change at Duroc, direction St-Denis.

Returning from the Marmottan you can take RER C, direction Massy/Dourdan.

The key to the metro is to get on the trains going in the correct direction. All information is written on the subway walls and easy to see. When you're changing stations look for the word "correspondance" indicating transfer.

I write down the route on a piece of paper before leaving in the morning so I can refer to it as I move quickly through the metro tunnels.

The Opera and the Marais are easily walkable. I would take the metro to the Jacquemart-Andre.

I would take the same route as to the Rodin but continue to Miromesnil, get off and walk the rest of the way. The other route is St-Michel to Strasbourg/St-Denis where you change for St-Augustin.

Try to avoid the huge transfer stations as you have miles of tunnels to walk. They would be Chatelet, Montparnasse, Gare de Lyon. Those stations that show many connecting lines.

Sometimes the easiest way to read the metro map is to find your destination and work backwards to find the best route.

Get the Metro AND bus map booklet. The buses will often go closer to your destinations than the metro--and you get to see Paris from the top.

It might not be true for you, latedaytraveler, but my DH and I often got turned around when we came out of metros. "Which way is north?" So he bought a compass and voila, problem solved. Of course you have to know what direction you want! LOL.

You should find the Paris metro very easy to navigate.

Have a smartphone or iPod touch? You can download metro/bus maps for Paris. I like MetrO and the official RATP.com app. You can also use the route planner online at http://www.ratp.com

I also find Google Maps really handy. All the metro and RER stations are marked. If you single left click on one you'll get more info plus the route the line takes shows up on the map.

Paris-ci is another handy app... shows you which metro exit you want to use.

TDudette has a good suggestion re compass... if you have an iPhone 3GS or later they have a compass app built in. Be careful using an iPhone on the street though... a popular item to grab and dash.

You'll be amazed at how easy this all is. ;^)

This looks like a pretty comprehensive and useful guide to how it all works, if you haven't already seen it:

http://goparis.about.com/od/transportation/ss/Metro_and_Buses.htm

Just remember to work out in advance which number/colour line you need and the endpoint of the direction you're going in (as it might be, "1(purple) Clignancourt/ change Strasbourg St Denis/ 9(khaki) Pont de Sevres".

And you'll see a local area street map in relation to the different exits, usually on the platform, or if not in the concourse area before the exit gates

We always take a little compass with us, for just that reason. It was a suggestion decades (really!) on the AOL Paris board!!

Wow! Such a great response.

Grandmere, thank you. I certainly can walk from Ivalides to the Rodin.

“If it's only one stop away, walk. And: Most of the time, changing trains is equivalent to walking one stop.” AJPeabody, I will remember that.

Kerouac (really love your photo essays and advice), I will probably just use the REC C to stop at Invalides to visit the Rodin, then take the same line to Boulvainvilliers and walk to the Marottan.

Thanks also to travelnut and Adrienne for you lengthy info/suggestions about using the Metro. As Adrienne suggested, I will walk from the hotel to the Rodin the first day, weather permitting.

Valtor, I appreciate your estimating the distance from my hotel to the Garnier as 1 ½ miles – that’s very doable. I will check out the site for other destinations.

Really appreciate ALL of your replies. Don’t have an I phone (yet) but will access those sites on line mentioned by Paris-Amsterdam and Patrick London among others.

I chose the HOTEL DAUPHINE SAINT GERMAIN at the suggestion of a friend who has been there twice in recent years. She assured me that the location is primo for “doing” popular sites and neighborhoods.

Believe it or not, I have been polishing my French which I took in school decades ago. I bought a French-English dictionary which I installed on my computer and constantly refer to as I check out Le Monde and Le Figaro – I have a long way to go! Not sure if I will be brave enough to venture a few words in the language but I have gained some fluency in reading French.

Merci encore....