There are three Internet sources of train tickets in France. The least well-known is probably Euro Railways, which we found the most expensive for our tickets. Then there's SNCF in French, and the SNCF-affiliate site in English, Rail Europe.
You might think you could use Rail Europe and find the same rates and schedules as on SNCF, but that is not the case. Even though Rail Europe is the English-language affiliate of SNCF, the prices are higher and not as many routes are offered.
Using the SNCF site and simply changing the language to English, results in an automatic switch to Rail Europe. When you try to change the language either to reserve the tickets or when you identify your home country, you are switched from the less expensive SNCF to the more expensive Rail Europe site. In order to use the SNCF site, you must navigate the site in French for the complete reservation. You must also specify France as your country of residence.
So using the SNCF site isn't the easiest way to buy train tickets because you're working in a foreign language, but it is definitely the cheapest. Only you can decide whether the savings are worth the frustration.
To use the SNCF French language site, it's helpful to have three screens available in your computer task bar. This Man in Seat 61 website page shows the same pages you will encounter on the SNCF site. It shows English translations for each page and provides a narrative to aid in each step of the process. It is also helpful to have the Babelfish translator site handy in case you run into a phrase whose meaning you'd like to double-check and, of course, you need the SNCF site itself. This may sound cumbersome or difficult, but we found the process easy after a few trial runs.
Here are some examples of price differences we encountered. Using the French SNCF site, we found prices for a one-way TGV train trip from Paris to Bordeaux for 44 Euros or roughly 63 USD per person. This ticket was refundable and exchangeable up to a day or two before the trip. There are also Prem (special sale) tickets available only on this site that offer considerable savings. There were Prem tickets available for 22 Euros/31 USD and 33 Euros/46 USD per person, depending on the time of day the train left the station, but these tickets were non-refundable and allowed for no change of plans. Compare those prices to the Rail Europe price of 73.50 USD per person, and the Prem fares become even more attractive.
Having said all this, you may be surprised to know that we opted to buy our tickets from Rail Europe. At the time we wanted to leave Paris, (Remember that the best PREM tickets are usually offered at off-peak times.) the Prem ticket offerings were only a few dollars less than the Rail Europe ones, and we felt the flexibility offered with the refundable tickets was worth the small extra cost.
Also, we would have had to redeem our tickets in a French rail station, and we understood from The Man in Seat 61 website that the rail station machines can be problematic for American credit cards. If we hadn't succeeded with the machine, we would have had to wait in a long line at the ticket counter. So, being leery of the ticket machines and wanting to avoid a long line, the idea of having tickets in hand was too attractive to pass up. We spent a bit more than anticipated, but it's reassuring to know we'll have the passes we need in hand to speed us on our way to the Dordogne.
To snag the cheapest Prem tickets, make your reservations early. Prem and other sale ticket prices are posted roughly ninety days in advance.