When we did it for our children we called and they sent us paperwork and then from there they has us call for a phone interview shortly after. They actually set up the time and then called us. My advise would be to make sure you have all the documentation you have at the ready. The more you have the better, so multiple dr diagnosis and evaluations is always better.

Also, have his official paperwork from doctor, therapists, etc. with his diagnosis listed.