I highly recommend this book. I set up a few reward charts 1-20, 20-40, 40-60, 60-80 and 80-100. I set up mini-rewards for every chart/20 lessons completed (pizza/movie night, trip to favorite jumpee place, cheap toy etc.)
Mini-rewards helped my son stay motivated with the material. This change made a "night and day" difference with my child. He now asks to do his lessons. I also made sure that I used LOTS of verbal praise, high fives, call family members to tell them how many he completed etc. He also LOVES to show his g-parents what he is learning!