It really depends on the person and what information you're providing them, if it's a confirmation through a deposit (e-transfer) or up to your ID, or a reference from another provider you've seen, or whatever the case may be. I had to go through screening for a few SP's (higher end girls), but the majority of the time I go to AMP for the new talent, and go in-calls for the splurge. Your poon depends on your budget, energy, time.
Everyone does things differently, I recommend going your own way. Go with the one that has the least personal details and use her as your future references, I remember joining the Apple Pie club and I quit their club in 2012, they wanted a work email when I joined and that job I was going to leave anyways as I was p/t with them, I was OK with that info as it just has my name (very common name, think Joe Blow, yes very common)...
For others, it may just simply be a Perb.cc handle and a log of your experience history, you can go for those first and bump up to the higher end girls after using this first gal as your reference. By using the two methods I mentioned earlier, you now have 2 references, unless you need a third, continue getting a third reference the same way. This should be all you need, again, as least yet acceptable info as possible.
Now, as another option, get this, you can practically go to the AMP's, repeat with them (the ones that you fancy and provide great service), get their contact info and use them as your reference. If you get two, three, or more of these, you're all set. You just need their permission to have them as your reference for future poon endeavors, that's basically it people. There really isn't a need for personal info, unless you're OK with it.