I use personal business experience and 3rd-party stories.
To stimulate a referrral, when I encounter a customer or prospect that can use "insert referral name," for their service I ask questions in order to guage their interest on the topic and the current steps they have taken to find a solution.
If they are receptive to a new solution, I will provide the following in one interaction:
- Business card
- "Blerb," of my business experience with that referral.
- 30,000 ft view of a previous (referrals) 1 or 2 info-minutes from P.C. that would apply.
I also try and make a warm connection between both parties to ensure that they are aware of what is being requested.