Hi Bubbles, welcome to PC. http://psychcentral.com/archives/e091001.htm is a site reference for how to select a psychologist. I think also, with ptsd, you would ask what kind of training they received specifically about PTSD, how long and how many patients they work with (or have) what types of therapy do they find works for this, what are the main things they would want you to know about PTSD, questions like that..

I think the main thing they are sure of is this is a real tough disorder, and they need to be in for the "long haul." They need to have firm boundaries. They need to realize it takes more time and energy commitment from them than most other disorders.

Whew! Well that's all IMO (in my opinion.)