In what concerns train travel, if you are flying in or out of Paris I suggest you take the TGV (Train of Great Velocity). You may want to consult www.IDtgv.com. This is an official site of the SNCF (the French National Railroad Company), that provides REAL discounts on train travel for certain destinations at certain times. As an example, the one-way normal full fare TGV ticket between Paris (Gare de Lyon train station) and Avignon (or vice-versa) is usually around 90 Euros (depending on how early you book) per person, however, via IDtgv it is between 30-50 Euros (depending on how early you book) on average…a real savings.
There’s a direct train to the Charles de Gaulle airport (in Roissy, just outside of Paris), however, if you take a city shuttle bus that will usually be cheaper when added to the reduced train price. You’ll have to compare when you’re ready to book, here’s the link to the different shuttles (you’ll want the one going to Gare de Lyon): http://www.aeroportsdeparis.fr/ADP/fr-FR/Passagers/Acces-Plans-Parking/Paris-CDG/Acces/Transports-En-Commun/ There is another shuttle (about the same price) that’s not indicated on the link’s list, but I can’t remember the name.
Be sure to try to use the French version of the site, as sometimes the English version will be more expensive. You can download and use the google chrome browser (www.google.com/intl/en/chrome/browser/) which has an automatic translation option and will allow you to see the information you’ll need.
Just for information vis-à-vis to “regional” train travel, you should NEVER take the TGV, as the time saved is negligible. Just take the regional express train (TER) and enjoy the scenery while saving a lot of money.
If you decide to rent a car at any point during your stay in France, I suggest looking at www.autoeurope.com which has some good rates. Equally, I suggest you do NOT pick-up or drop-off your rental car at an airport or train station, if you’d like to save money. You pay an extra fee (tax) if you do at all train stations and airports in France. There are off-site offices of all major rental companies VERY close to the train stations or airports. You should ask your rental agency where is the agency away from the airport or train station where you will be picking up the car.