The French rail system (SNCF) is extensive and very efficient. We often use it to get from Paris to the beginning of our walk and back again at the end.
The TGV (high-speed train) network is more expensive than normal trains (TER), but saves time and is quite an experience.
The first step in planning a trip by train or bus on the SNCF network, is to check the SNCF timetable. This lists every possible trip, even those that cannot be booked in advance. However it does not give prices.
The next step is to go to SNCF reservations, where you can buy your tickets (when this can be done in advance), and print them at home. That way you can step straight on to the train without queuing up at the ticket counter.
If you do not have access to a printer, you can pick up your booked tickets at the railway station, but you must show the credit card that you used to buy the tickets, to validate your identity.
Booking in advance gives you the option of buying a “prem” ticket. Prems are much cheaper and, if available, are listed in green in the “Non exchangeable” column.
They can be purchased from around 3 months before travel, but there are only a limited number available on each train, so book early.
If the tickets for your train are not yet on sale, you can subscribe to receive an email notification when they become available.
An oddity of the French rail system is that tickets (not ones that you print out yourself) must be “composted” before boarding the train.
This means getting them punched in a little yellow machine at the entrance of the platform.
Tickets are always checked by a conductor on the train and if they are not composted, you will be frowned on, or even fined.