• Make it easy for someone to bring up what you do (by changing the nature of the service or product).

• Give your best customers something of real value to offer to their friends (a secret menu, a significant gift certificate). Once you do that, not giving that gift to a friend feels selfish.

• Paying me to refer you rarely works, because you’re not just asking for a minute of my time, you’re asking me to put my credibility on the line.

• Understand that low-risk referrals happen more often than high-risk ones, and either figure out how to become a low-risk referral or embrace the fact that you have to be truly amazing in order to earn one.

and

• Be worthy. Not just in the work you do, but in your status in the marketplace. I’m far more likely to refer someone with a back story, someone who’s an underdog, or relatively unknown. That’s why saying "thank you" in deeds (not so much in words) goes such a long way.