We got a Paris Visite metrocard, which I believe covers you for some of the light railway too. You can get 1 day, 3 day or 5 day one. We got ours at Waterloo Eurostar terminal for £18.50 I think (5 days) , but we could actually have got it cheaper through Thomson's as advertised in their City breaks brochure, for £13.50 ! So shop around.

There are loads of buses too, and if you are staying near the river, there is a "Batobus", which is literally a "Boat-bus" and stops off at the major tourist attractions. Not fast, but more scenic than the metro! You can get 1 day, 2-day etc tickets for this too.

We didn't use any taxis while we were there.

have fun

The RER B Metro line serves the CDG terminals and will take you to Gare du Nord station in Paris. You can catch the free green shuttle from the terminal 1 arrivals & shopping level to take you to the station to catch the train. The one-way fare costs just under €8. There is also the RoissyBus that serves the CDG terminals and ends up at the Place de l'Opera in Paris and is about the same price as the train. Both of these options are covered by the Paris Visite travelcard Acorncup mentioned. Choice between these or a taxi might also be affected by how much luggage you have with you as negotiating metro stations and stairs with a lot of luggage isn't much fun. I think a taxi would cost ~€50.

If you decide on the Paris Visite option and buy a 2, 3 or 5 day pass, be aware that it is only valid for consecutive days from the first day of use. Cost also depends on which zones you want to visit. I think the prices Acorncup has quoted must have been for Zones 1-3 which only cover central Paris. You would need to buy a pass that covers zones 1-5 to include CDG airport (it also includes Disneyland Paris and Versailles). Normal price is €16.75 for a one day pass up to €45.70 for a 5 day pass.

Another cheaper option is the 'Carte Orange' weekly travel pass you can buy at RER and Metro stations. This is very good value for money but the first day of the week always starts on a Monday and the pass runs out the following Sunday. It's a pass that was mainly intended for Parisians rather than tourists but anyone can buy one although it does requires a passport-size photo on the card (to prevent pass sharing). The big plus is that a weekly pass for zones 1-5 is only €27.65 which is only slightly more than a two day Paris Visite pass! Between Monday and Wednesday, you can buy a ticket for the current week. Between Friday and Sunday, you can buy a ticket for the next week.

HTH
Rob

robbo thanks you know a lot more about it than me!!! yes, we did just go for the central area, which covered the ..er....centre...including Gare du Nord.

Just a couple of points I've thought of, though...

1. I gather there are scams going at the metro stations where locals offer to help you buy your metro card, then take the full price of the card but just buy a single ticket (or something) so make sure you buy your own ticket if you haven't already got one before you arrive.

2. My Paris visite card got bent while I was carrying it in my pocket, which meant it stopped working on the electronic gates, which was rather embarrassing. it was OK in the daytime, as the attendant would let me in/out, but tricky at night at unmanned stations. (tried to re-use my hubby's card to let me through, but the machines wouldn't let me!)

Yes, I found the Metro very inexpensive, reliable and safe. Even at night. Easy to use and very fast!