We have found it VERY useful to have a therapist familiar with gifted kids and their characteristics. For one, they don't pathologize what can be normal gifted quirks.
There are a couple of good articles about how to find one, and how to interview them before starting on the SENG website. Webb's book (A Parents' Guide to Gifted Children) also talks about it.
Some random ideas: local gifted school (private), or referral from somebody from the gifted program at the public schools, regional gifted association or groups, local SENG group, etc.
