Its quite a challenge when using sites like Alibaba, as most people end up using Western Union and the feedback process on those sites is a little different than usual.
Heres what I usually do
- Make sure that the user has been around for a while
- Ask myself if the transaction makes sense. If the seller is in China, they shouldn't be telling me to send WU to Nigeria
- Start with a small order
- Google the person's username. Sometimes people will post complaints about them in outside forums.
Overall, I find the best way is to start with a small order and work up from there. It isn't fool proof, but it'll weed out many of the scammers and minimize your losses.