Sometimes the best referrals are made from people who you didn't even do business with. 

I remember a year ago helping out a lady with making the best informed decision on her health insurance plan.  And although we did not do business together, she was incredibly appreciative of the fact that I was just there to help advise her.  

Fast forward a year later, she referred me to several of her clients.  These are the best type of relationships to me because it tells me that she trusts that I would have her clients' best interests at heart.  

Even moreso, her clients have also started sending me referrals as well!