I like to make screening easy and to give plenty of options. Usually any of the following will work. Two of the following almost certainly will.
A LinkedIn profile with a fairly recent photo?
Professional email? I have a second email account with no connection to the hobby for that.
I could discretely call and ask for you at your desk through the automated attendant, dial by name system or receptionist. Even if you're not there, if your professional voicemail is accessible remotely, I could and leave a message for you to retrieve.
Maybe there is a mention of you or a photo of you on an organization company website someplace?
Is there an article written by you or about you that would also lead to a photo?
Active memberships in P411 or RS-AVS works. Screening through Private Delights and Avenue X also works, with the caveat that there has been interaction between you and other companions there. Other boards with a similar set up may be considered.
How about references from two or more established companions who you've met before?
I could try to Google you; sometimes that works. I could even try to find you on Facebook.
But anything like that usually works.