I got names from people I trust, then researched them on the internet (and psychologytoday was particularly helpful). Narrowed it down to about 8 people, and did a phone interview. 2 or 3 said they weren't taking new clients or weren't available at the times I had available or something that knocked them off the list. I asked about what their training was (CBT, PCA, Jung, Gestalt, Gottman...?) Then I made appointments with 3 of them (and told all three what I was doing and they said they were willing to participate) and had a session (that I paid for) as if I was starting with them, and then chose one. I'm really glad I did it that way.
It was a bit long of a process, and at times I wanted to speed it up. But I'm really glad I didn't short circuit the process. I learned a lot. One of the session/interviews was very revealing, and I thought she was the one I would want. She had all the right backgrounds and seemed very warm. I liked the session with her - until I asked a question at the end and she felt challenged and I didn't even think I was asking a challenging question - just informational. She took it as a challenge and wouldn't answer! I didn't choose her.