I would simply ask the staff 1) where they were trained in fitting and 2) can they show you a basic breakdown of the process.

When I got my fitting done, he had a logbook where he kept all my records so we always know where the "start" is that he made notes in the entire time. Other than just putting me on the bike and playing around with the string and pendulum thing, he measured my hip flexors and shoulder and all other various body parts off the bike. He was sent by the shop we have here to go learn how to fit professionally as well at one of the various schools out there. I was extremely satisfied with the thoroughness.

You could always do it yourself as well:

A walkthrough that has been posted here before.

EDIT: sorry for the rambling sentence structure. I don't have time to fix it at the moment but I promise I'm usually more coherent.