Getting around Paris?

Just Yahoo Paris Metro and you will get good maps for the paris metro and all kinds of other information, including passes, BTW The information received from an answerer about the RER trip from the CDG airport is 100% correct. You should know that Cachan is not actually in the city of Paris. It is in a southern suburb just outside the city line.

Paris has the advantage of being one of the few capital cities in the world that is small enough to walk from place to place .. and if you do there is so much more you'll notice ! As far as the airport to the city goes .. Taxi !!

Contact the hotel and ask them to organise a lift for you from the airport terminal to the door of the hotel. You'd be sharing a people carrier-type vehicle with other people going to hotels in the same area of the city, and while you'd be paying more than you would for the metro or bus, it's still a lot less than a taxi, very reliable, and you'll be taken right to the front door of the hotel. All the driver needs is your name and the hotel you're staying at, and they'll meet you in the Arrivals hall with a big sign with your name on it. A doddle! You can pay the driver when you get to the hotel, just remember to have some Euro on you. It's usually a set price per person. I've done this and strongly recommend it. Just e-mail the hotel, and ask them about it.