How to know that some traders in china are legiitimate or ot?

I am placing some orders through the web for some bulk materialsnand I have tons of emails from ppl in china, all of them are claiming that they are manufacturers , but i doubt that, because i feel they are all traders, how can i know the elite or legitimate ones from fraud one???

Please help

Some Quick Tips: Verify that they...
*accept credit cards over a secure server;
*have trust seals that are active and legitimate;
*list a physical address (not just a P.O.); and
*list a toll-free number and a live person answers/returns a call.
If these conditions are met, search for reviews and complaints. If they have more good than bad, chances are better that trader is legitimate.

Source(s):

-Questions to ask before making a purchase:
www.EConsumer.gov/english/resources...
-Researching a store before making a purchase:
www.OnGuardOnline.gov/articles/0027...