Happy clients are the best branding. I built my business almost exclusively on referrals, which not only filters out clients that would not be a good fit, but also provides reputational policing for agreements: The option of a client considering not to complete their side of an agreement has additional negatives due to the relationships involved. Likewise my service/product reflects on the referer, as it were, providing me another incentive to deliver massive value. And the referer gets the bonus of having been part of a successful solution.

Win-win-win.