+1 on the Lee Parks' Total Control book. The chapter on 2 up riding is very good. I had my daughter riding on the back this weekend for the first time. She's been on the back of my wife's cruiser, but never my bike.
We did about a 10 min pre-flight walk through of what she should expect.....lean when I lean, don't push on my back when braking, balls of the feet on the pegs etc. I forgot to tell her not to shift her weight when we are turning
, but she figured this one out on her own after that. She did so well that I took her on some curves at a mild pace and had so much fun, she didn't want to get off when we pulled in the garage.