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.