The big thing is making sure he builds a notebook of things to remember from each step AND does ALL the problems in the book - including the very hard ones - he should be intrduced to the idea of doing things in his head at night or while walking.
No offense, but I think you should make sure that he will NOT do ALL problems if he understands the concept. There is no reason to do every single problem in the book. Yes, make sure that he does the most difficult ones and he understands the concept, but feel free to skip simple exercises if the child already mastered the subject. An average student needs many more repetitions than a gifted one. You don't want to end up with a child who resents math and is bored because he had to do every single problem.
This is definitely the path we will follow with DS5. Singapore Challenging Word Problems are nice, but only the challenging ones. The same goes for Zaccaro.
