Try to verify their address through Google maps and the white pages.
Welcome to WholesaleForum.com! Sign in or Register Free to benefit from our full range of free services1.) I perform a Google search that includes "Company Name Co Ltd scam". Usually, there shouldn't be any returns with a negative feedback. If you see at least one, maybe it's a scam. It could also be one of their competitors performing a negative PR campaign against them.
2.) Bookmark websites such as Main Page - aa419 who have a compiled list of all websites branded as a scam.
3.) You can start threads asking about their credibility on numerous trade forums like this one.
Try to verify their address through Google maps and the white pages.
Talk over the phone, check to see if they use a free email service, and see if they will fax you any required documents.
Great thread, I hope you don't mind me taking example by creating a sticky thread containing a summary of all the main verification methods ... just to keep it orderly, we can then continue this discussion in that thread?
I have started it at this link.