My usual “Thank You” is a free session, and it is always appreciated.
I have also given a gift certificate for a session with a reflexologist. This was a great hit with those who feel that this is ‘pampering’ and who would never go out and get it for themselves. The reflexologist in question is in my network of people I refer to, and this in turn has generated reciprocal referrals.
For referrals from current clients, I would offer a free session regardless of the commitment from the referred client. I view it as my job to close the client who has been referred. For former clients who refer new clients, I think the appropriate gesture would be something to the effect of a gift certificate of equal value to half the rate of a single session.
The only thing I give away free is a consultation. I encourage my clients to let their friends and acquaintances know that I appreciate very much their referrals.
Doctors, lawyers, physical therapists, group fitness instructors don’t generally give away their services for free.
Have you ever thought about having t-shirts made up and giving that as a token of thanks?