I've done a little research but have some basic questions.
1) Any recommendations on providers in St. Louis?
2) Other than TER, CL and Eros how can I find providers?
3) How can I tell a legit ad from a LEO?
4) What are the standard verification procedures?  Do i really need to give out personal information?
Thanks in advance!

However, St. Louis is one of the cities that can be researched on the Review Section.  Go to Reviews and click "search reviews", then set the city filter for St. Louis and also set the filters for the kind of provider you want and see what pops up.

It will help if you are a VIP member so that you can read the gal's reviews too.

As for item 3, it is not easy to discern LE from legit, so stick with well reviewed providers.

Verification is as per the gal's requirements which will be on her website, but having a recent reference is usually the best followed by membership in a screening servie such as Roomservice 2000 as well as personal information such as name, address, work place, etc.

Best of luck.

Any public forum can be accessed by LE.  However CL is the easiest & most conspicious...  often LE target.  
Experienced hobbiests occasionally take the risk...  and there are some hidden gems on CL...  but can you stand the risk.
skb