"Packed full of getting it done"
Jantsch has written a fantastic book about building a business based on referrals. The book is packed with idea after idea for helping your customers refer you to other customers.
If you've already read "The Ultimate Question" then this is the other half. Why just ask how likely are you to recommend us to a friend or colleague if you don't then ask them to actually get up and make that referral.
My current fave: "You're going to like our product so much that in 30 days I'm going to come back and ask you to introduce me to three friends or colleagues that could also benefit from our product"