Accelerando Technique Books

[jesspiano]

I just bought the Acclerando Technique Books 3 & 4. I'm really excited to use them! I've been struggling to find something I liked for early intermediate students, and this looks really appealing.
I'm just wondering if any one else that has used them has any advice on how to approach the excercises? I definately will have the student transpose them, but how do you decide which keys? We don't have time for all 12! It would take up all of her practice time. Plus, she'd hate me!
The book suggests playing at 3 different speeds. Any thoughts on what is most effective?
Also, I'm wondering what to focus on technically. I don't want her to just be playing the excercises mindlessly with the metronome.
Thanks!