It is unfortunate that most TS provider don't really pre-screen their clients, that's because we have less clients than GG, also it is very easy to pre-screen if you have an agency you work for who would do it for you, but since most of TS providers work independently, most of us do light screening and using our instinct, most of the time we could tell how nice or respectful the clients are by listening to them on the phone, the way they talk, the way they greet and also the way they writing an email. So far I have not missed my instinct even for the bad guy i've met in SF, I didn't listen to my instict.
People have different personalities, but they do have similar habits, and that's how I can tell 
I really hope that I can maintain that!
For me, getting clients from Date-Check and Preferred411 is not guarantee they are trusted clients but rather safe since they have information there. In fact, I had few clients who have made appointments from those sites, they even gave me their username and number, after a few exchange emails, they did not show up to their appointment, not even cancellation, I'm not sure if they forgot or lost interest and decided to blew it off. But i usually let it go if they are pass the time where they had to call to confirmed!
I think Date-Check and Preferred411 is good for those hobbyist who want trusted providers. But most of them haven't put trust in TS providers that much!
I have read a few gentlemans on the board who were outrage by TS providers who asked for their complete information such as ID, etc, and also a gentleman who mention he would not mind to be pre-screen only by trusted provider which is make sense, and how many trusted providers out there in the field, less than GG.
But until the gentleman have respect for TS Providers who prefer to pre-screen, it is unlikely that most of TS would join any pre-screen site.
They still double standard TS providers I must say, and I saw lots of GG providers who blurr their faces in almost their ad's pictures, and they are still acceptable and Hobbyist don't mind to pay thousand of dollars, but if TS blurr their faces on their add, it's a red flag for Hobbyist, I said this base on the conversation I've read on different TS board!
Hopefully in the future, those who are interested in TS provider will be willing to be pre-screen.
Last but not least, the TS hobbyist hesitant to give their info to TS providers by nature, some of them still think TS and GG are not equal maybe until the society accept TS as a third gender or as woman itself... 
xoxo
Posted By: veronicacross
Hi BigNation, this is a great question, thanks for asking!
I am on, and use, Date-Check (and Preferred411) regularly. Like Rachel mentioned, just search for names containing "TS" and sort and there are quite a few of us. The good thing is I sincerely doubt you'll find any fakes on there, however there's not a ton of us, admittedly. There are most likely 2 reasons for this. 1. As Rachel said, unfortunately many TS providers don't pre-screen like most gg providers do--and that's a whole 'nother discussion in itself. 2. D-C (& P411 & RS2K) don't make it explicitly obvious to us trans gals that we're welcome to use their site--but actually we most certainly are. Personally, I like D-C & P411 and have met a lot of great guys through them with zero hassle.
Happy hunting!
xo,
Veronica