The Game of Solitaire
If you wish to practice alone, take the Code cards and shuffle with the words up, noting the time when you begin. See how quickly you can go through the entire set, naming the numbers for the words. Then reverse the process and name the words for the numbers.
Now try it again and see if you can cut a few seconds off the time. Keep a record of the time required to go each way and strive continuously to reduce it. Keep at this until you can go through the 100 cards in two and a half minutes or less.