Train From Airport
 

Is it best to take the TGV or RER from CDG into downtown? Never done it this way, and I'm not sure what is more convenient? Any help would be great. I'll be at the Sheraton in Terminal 2.

IIRC, the hotel is right on top of the CDG2 train station. RER would intuitively be cheaper (haven't checked) and probably more frequent than TGV. I think both depart from the same station. If you can schedule it, the limited/no-stop RER service between CDG and central Paris (Chatelet-les-halles) would be the best.

The southbound TGV's stopping at CDG do not go into Paris, with most bound for Lyon and a few, IIRC, for Bordeaux.

The RER costs €7.70.

When you exit the hotel lobby, immediately in fromt of you will be escalators leading to several lower levels. This is where the RER trains leave from. On one of the lower levels is a ticket office where you can (if desired) buy one of the multi-zone passes (Paris Visite) for one or more days. Because these allow unlimited transfers on both the RER (regional commuter trains) and the Metro (city subway trains), they can be real bargains. The site below gives lots of additional information:

http://ratp.fr/

(Once you're on the English page, click on the PARIS VISITE link under the RATP FOR EVERYONE column for prices and information)

The RER is cheaper and more convenient from the point of view of destination options.The fare is 10 Euro one way to the centre say Notre Dame and E 6.2 each if you buy 10 tickets -handy if you do not want to stand in a long queue each time you travel into town .I agree also re using the express trains after dark .
Ozflier