Sourcing your suppliers from B2B platforms, such as Alibaba, Global Sources, and Made in China. Every platforms has some dishonest trading companies and it is not easy to identify if you never cooperate with them(Tip you should know, some forums would post names of the undesirable companies). If you are interested in some companies, you’d better gather as much as information to ensure they are legal and reliable.
Attending local trade fair in China. Although you cannot make sure all the companies are reputable, at least most of them are reliable and powerful. There are two large trade fairs in China you should know, Canton Fair and East China Fair. Various factories and trading companies on these exhibitions and most of them can speak in English, but many have limited spoken English skills. If you want to get further communications with them, you’d better remain an translator to help solving unnecessary troubles.
At last but not least, if possible, visit their factory personally. You can effectively judge if they have enough capability to fulfill your order, and it can avoid middle man and scams effectively as well.