Some companies offer an E.A.P. or Employee Assistance Program where you can call and speak with a provider. Sometimes speaking with someone over the phone might give you an impression of the provider. You can also inquire about the providers' expertise - find out if they regularly treat folks with the diagnosis you have or not. Inquire about therapy approaches - etc.

When I searched for a psychologist to help my son I was looking for someone who specialized in children on the Autism spectrum as well as experience with PDD. I was also specific about wanting to get assistance with behavior mgmt techniques for both home and school. Not every psychologist is familiar with behavior issues associated with autism, pdd, etc

That approach worked for me and I've been very pleased so far.
Good luck