Require either a TER,Date-Check, or P411 membership. This will get you serious hobbyists who will be more inclined to pay a premium as compared to prospective clients who aren't as serious. Another is to require two or more references.

...is to refuse to see "newbie" clients (for now, until you learn more about screening), and require two references from well-reviewed providers.  Pay for VIP on TER if you can, as it will be worthwhile for you when cross-checking the providers' reviews and making sure their reviewers are real guys (especially if the provider only has 5-6 reviews, you will want to check and make sure the reviewers themselves are legit).  Email each provider and ask for a reference.  You will need to show the providers some verification of yourself, such as a link to your website and your reviews (if you do not have any just explain your situation and link to your website instead).  Don't meet with guys who don't have reputable references that you can verify (...for now, until you learn more about other ways of screening).  Date-Check and P411 are good resources, but you won't be able to use them until you have some reviews or referrals from established clients.

Also please run the names/emails/phones of the guys who contact you through a blacklist search just to make sure they aren't known to be cops, rapists, etc.  I will PM you the name of the most popular one we use.  You will need to submit to a verification process to gain access to the blacklists also.

Good luck! ~Zoey