Le Metro

In the States, if you're in a city that has a metro system, in order to get to the trains you insert a ticket to go through turnstiles. This is how they make sure everyone pays (for those of you who have jumped them).

In France, they do not have these turnstiles. Instead, they have validation points, which are machines that punch and time stamp your ticket. In most french cities, you have an hour to use the ticket. In Paris, the ticket is valid until you 'exit' the metro station.

Hint: The validation machines are rectangular, stand alone machines and are many times orange. Observe others the first time so that you know what to do...then it will be second nature.

Make sure you validate your ticket before hopping on the metro or a train. To avoid intimidation and fines, it is crucial!

On all trains (underground and aboveground) they have controleurs who get on and off trains just to check whether you have stamped your ticket and that it is for the valid day and time. If you are caught without getting it validated, you will be charged a fine on the spot. (These controleurs are not just in France, but throughout trains in all of Europe).

In addition, at metro stations, on your way up from the escalators to exit, they sometimes set up checkpoints where there are several controleurs and guards that stand in a line blocking your exit until you show your validated stub.

So, words of advice:
1) Validate each and every ticket when riding a train.
2) Keep your stub until you have left the terminal.
3) Make sure you buy the correct tickets and do not hesitate to ask for help. If you accidently buy a student ticket (because it is cheaper), and you are not a student, you will be fined.