I use P411.No problem so far.

Date-Check.com or Preferred411.com they are both verification sites and you can also search for ladies in your area on these sites.
Good luck!

Depending on where you hobby, not all of the verification services are used by providers nationwide.  For example, "Room Service 2000 " is very popular in the mid-west region and many providers, especially in Chicago, often require RS2000 for verification.  I'm based in Chicago, so I'm a member and I've had no problems with their service.

The other 2 popular verification services are Preferred411 and Date Check.  I've used Date Check when I traveled to the west coast.  I'm not a member of P411, but I believe it's also popular on both the east and west coast regions.

Also, even if you belong to a verification service, some providers will also request provider references as well.

If you don't want to use a screening service, you can consider providing your personal information to a well-established, careful, reviewed independent provider who will not require references but who may be willing to give them.  From there, if she will give you a reference (I usually limit my requests for a reference to the number of times I have seen the provider), you can have a second provider to give you a reference for your next time.

There is always risk, but I believe the risk in providing personal information to a known and reputable provider is minimal.  In more than a decade in this hobby, I have not encountered an instance where an independent provider's client information was made public.  Agencies, yes; Eliott Spitzer and David Vitter can attest to the vulnerabilities of agency lists.  And if you are a public figure, you are taking a HUGE risk in any kind of non-marital sexual activity.  But the ordinary client has a much greater risk of a car accident on the way to the incall location than he has in the misuse of his name or employer.

There are two perceived risks from disclosing your personal information: (1) public disclosure in the event the provider is arrested or otherwise investigated by LE; and (2) provider blackmail.  There are instances of the former happening, but as I mentioned, I know of know documented instances where an independent provider's client list was publicly revealed.*  And if the provider does rigorously screen, that only assists in your protection.

As for the second risk, again, I have simply never seen it happen.  I can't rule it out, but it seems to be wholly improbable, especially for a well-reviewed, established provider.  Such a woman wants repeat clients, and wants a good reputation.  You would have to be really rich and really vulnerable for blackmail to be remotely profitable.

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*The "Sugarloaf Madam" episode in Atlanta, where a provider was alleged to be involved with drugs as well as sex-for-money, is as close as I can recall where there was such a risk.  The media claimed there was a "black book" and there were articles suggesting it would be made public, but it never was.