Paris Gare Du NORD RER ticket purchase

You can buy a carnet on board the Eurostar or at the information desk @ St Pancras. You pay a bit for the privilege, but it saves fiddling about with machines, queuing etc on arrival.

A US chip and sig card works fine in the automatic machines for the Paris transport system. When you get to the part where they say 'enter pin' you just hit continue and it will work. I recently charged my Navigo for a month doing this on a machine, and you can buy a carnet of tickets the same way. The machines have an English option and what you want is '10 t+ tickets'. I don't think they use the word 'carnet' in the English version; carnet is just 10 of the same ticket. The ordinary tickets work on bus, tram, metro and RER within Paris (and the metro wherever it goes, sometimes just outside of Paris) Getting a carnet on the train is also a reasonable idea.

How many are you? Why not take a taxi after such a long journey? It is a five minute taxi ride....you will be paying about 8 Euros in metro tickets plus the aggrevation of changing at Chatelet...an unpleasant location to say the least.

I do not recommend arriving without any cash. Exchange at least 300 to start your trip so you don't have the stress of going to an outdoor ATM upon arrival.

There are 4 of us. We will be arriving around 13:00. I was looking at Google Maps and it said that at that date and time a car would typically take 20-45 minutes. Thinking about it some it does appear that a taxi would be easier due to the luggage (one carry on per person plus a couple of shoulder bags).

Couple of things -- A carnet is a discount packet of ten, single ride ticket that can be used by anyone. Second -- extremely important -- keep track of that ticket from the time you use it till you completely exit the subway/metro system.

You probably will find that the Am Ex is not widely accepted. I generally leave mine home and depend sole on Mastercard or Visa as the preferred cards in Europe.

I buy a carnet from a ticket machine. It's not a book of tickets, just ten individual tickets for 14 euro. For the trip you describe one ticket will do for each passenger. Be sure to hold on to it through your entire trip. Sometimes you need it to get through the exit, other times you may run into inspectors who want to see your ticket. I've been inspected once. About five inspectors were in a fairly narrow walkway asking to see everyone's ticket. If you don't have the ticket you are using for that ride, I understand it's an on the spot fine. When you leave the metro at your destination, get rid of the ticket so you don't confuse it with your other tickets. There may be a way to tell a ticket has been used but I don't know it.

I use cards (credit and debit) with a Visa logo pretty much exclusively in Europe. I bring an Amex but only for rental cars because my card has such a good rental insurance option.

Actually, the change at Les Halles is very easy. You just take the escalator (or elevator) up to the mezzanine level and walk over to the escalator down to the platform for the west bound RER "A". Should be marked "Direction Cergy/Poissy/St Germain-en-L.aye".

This schematic shows the platforms at Les Halles. You arrive on the top platform if you are on the blue RER "B", or the second from the top one if on the green RER "D" from Gare du Nord. You have to transfer the red RER "A" westbound, which is the bottom platform.
https://en.wikipedia.org/wiki/Gare_de_Ch%C3%A2telet_%E2%80%93_Les_Halles#/media/File:Gare_de_Chatelet_Les_Halles_track_map.svg

If you decide to take a taxi, be aware that if you take a "short trip", the meter will read 7 EU for 4 passengers. This is the minimum legal fare that the City of Paris has instituted.
There are no fees for luggage in the trunk.

It's a good idea to ask the taxi if he takes credit cards before you get into the taxi.
It's also a good idea to print out the complete address of your hotel - Postal Code included - so there won't be any confusion.

A carnet of tickets (10) now costs 14.50 euros and are " valid for transfers within 1 hour 30 minutes of first use, but only between certain methods of transport and depending on the type of transport used."
This is a great site for explaining transfers and more about the metro system.
http://parisbytrain.com/paris-metro-tickets/
When you enter the metro and put the ticket in the machine it comes out with printing on the back that says the date and time you entered the system. Sometimes the ink is faint but it's there. It's good to note the time if you think you will be at a location for less than 90 minutes since you could then use the same ticket to get back on the metro for another trip somewhere.

This is not true. The metro ticket is not good for 90 minutes; it is good for one ride. Once you exit the system you cannot use the ticket for another ride. where the RER and metro cross you can exit the RER and then use that ticket to enter the metro at that station; the machines will know you are transfering since these are magnetic tickets that record the information. But a ticket once used on the metro and exited to the street is done and will not be accepted for another ride.

At CdG you will buy an RER ticket to your destination near Charles Etoile. It will work for both the RER and, if needed, the Metro. Standard fare is 10 euros. To exit RER B at Paris Nord you will need to use your ticket to open the gate, just as you did to enter the platform at the airport. Ditto for the second train so hold on to that ticket. Never discard any RER or Metro ticket until you are outside the exit gate. There are attended sales desks at CdG and you can ask for a ticket to your destination and offer cash or credit card. Sorry; there is often a lineup. Why not get some euros from a ticket machine at the airport? Sometimes an ATM will be located in the luggage area where you will almost certainly be standing around waiting for your bags.
The RATP system of rapid transit has plenty of info on its website http://www.ratp.fr/itineraires/en/ratp/recherche-avancee

The Getting Around section includes an interactive planner to show you routes and make rather generous estimates of the time required.

Thanks everyone for the great information. I think for simplicity sake we will take a cab due to the luggage and convenience of being dropped off directly at the hotel. I'll have the address of the hotel printed and make sure that the cab takes credit cards. I'll get Euros from an ATM as soon as it is convenient and feels safe.

I just ordered a Capital One Venture/Visa to try for the trip. I use the AmEx a lot because it is Hilton branded and the points and HHonors program work better for me than airline miles and my backup is a MasterCard. I'll investigate a little more but likely leave the AmEx home and just bring the Visa and MC along with my debit card for the ATM.

This was my first post in the forum and apprecite that you gave me a lot to think about ... Just what I would exect from a Rick Steve's crowd.

To exit RER B at Paris Nord you will need to use your ticket to open the gate, just as you did to enter the platform at the airport. Ditto for the second train so hold on to that ticket

Not true. At Les Halles you are transferring from one RER train to another with out exiting the RER system. Like I said, up one escalator and down another. Yes, you will need your ticket to exit the system at Etoile.

Yes. You need the ticket to exit the RER system since it is metered (the metro is one size fits all so you only need the ticket at entrance -- and retained in case you get ticket checked) but while in transit you can transfer from one RER to another without leaving the system.

You did not ask and have decided to take a taxi but in case others are thinking about this trip, you could take Line 2 from La Chapelle and avoiding having to change trains. You would walk to the back of the train to exit and take escalator/elevator up one level (RER concourse) and then follow the signs "Métro ligne-2, La Chapelle". Also, if you want to get there faster or if there is an issue with the RER Bon your travel date, you could take RER E from Magenta and then switch to RER A at Auber. It's a touch faster -- 2 stops on the RER versus 3. By the way, I totally agree with the OP's decision to take a taxi. It's what I would do. However, I would make sure that I have some euros before getting in the taxi line because some taxis in Paris do not take credit cards.