For the first operating session, which was sort of a test-session, I used small handwritten freight cards. I've now made 4-cycle freight cards for 28 cars which will be used for op session #2. This isn't nearly enough cars, but the first few sessions will be a learning experince anyway, so the trains will be a little bit on the short side.
The red number in the top right corner indicates which cycle the freight card is in. For the next session I'll arrange all the cards so the red '1' is in the top corner. After four sessions we're back to the beginning.
Here's the back side of the card shown above.
My car cards are of the norwegian FREMO-standard. They are nice and small and fit nicely and the palm of your hand. On the back is a picture of the car...
... and on the front is a small pocket for the freight card.