Your ticket tells you the train number, the car number and the seat number. What you can’t know until 15 minutes ahead of time is what platform you are on. Everyone just sits with their café and baguette watching the big screen, which has information about the trains that are present, and the trains coming up. It’s boring, but you really can’t take your eyes off of it (especially if you are a tourist) or you might miss your train. It has the ready-to-snooze factor of watching a pot boil, combined with the now-or-never anticipation of waiting for the gun to go off at your first Olympic race.
Mine was platform 4, to the north. I quickly followed signs down to #4, and then looked at a short and wide screen that indicated where to stand to get into the correct car. I stood in what I thought was the right place, but then a train went by and stopped maybe
100 yards down from where I was standing. Hoards of people ran to that train. I was confused. It’s not time for my train, but maybe I need follow everyone else.
It never hurts to look confused. A kind French woman saw me and said “deux trains!” She held out two fingers, indicating that another one was coming. She asked to see my ticket, and confirmed I was in the right place.