If you are planning to use insurance, start there. If not, then you have to figure out what your own parameters are. For instance, beyond insurance (absolute requirement for me), location matters since I would be going generally from work, end of day, traffic, etc. How far can I reasonably travel? Then I might run some general searches within that area for therapists. I know what gender therapist I prefer. I know what credentials I prefer. Once I get a few names, I'd explore their webpage if they have one. I might read reviews although I haven't found they are very helpful for therapists (usually are very few reviews unlike medical doctors where there are usually quite a few). Then at that point I'd call whichever therapist seems to most closely meet my criteria and make an appointment. The only real way I've ever found to really know is to simply sit down with them and get a feel for their style/personality, etc. (that goes pretty much for any doctor I would go to also).

Once I have that first session, I've always just gone with my gut (which has been pretty accurate). I usually knew almost immediately if a therapist was going to be a good fit for me. There were a few that I gave a 2nd or 3rd shot at just to be sure I wasn't jumping to conclusions too soon, but inevitably if I didn't feel it that first session, I didn't stick with them (and never regretted not going back to those I was wary of or unimpressed by).