Your best bet might be to look at some other providers web sites and see what they are asking for on their contact forms.  One of my regular ATF ladies asks for first and last name, city and state that you are from, business phone number and a photo ID when you arrive at the appointment. She also requires at least one reference from an active indie provider that she can contact via phone or email.

Reference from other ladies that you know (other local ladies) is the gold standard.

Other ladies you can validate that they are ladies is also worthwhile.

For real newbies, employment info, and calling their to verify he works there is what typically happens next.

Ask for board handles so you can see their posts (looking for history of hobbying).

You are trying to find out:
1) He is not LE
2) He will be a good date (not NCNS, won't ask for strange stuff, etc.)

Good hunting