Speaking Mandarin (as Drulee points out) would be an absolute bonus although not as critical as a few years ago, many young Chinese are now coming out of Uni with a very good working knowledge of English and companies that deal with the West are snapping them up as sales reps.
My advice is to go to one of the trade gateway sites (D.H.Gate.com for instance), there are very many of these and each gives you access to hundreds if not thousands of sellers.
You will first need a working idea of what you are in search for as general browsing of these sites will have you lost in hyperspace for weeks.
Once you find a seller that interests you, do not contact them on the trade site, instead follow the trail back to their home (this may require a fair bit of Googling), this way you get to see first hand if they are a large manufacturing group (best option) or a mum & dad tin can alley seller.
This is not an easy task, it can take many months of dedicated searching to find what you want, but then you might get lucky and stumble on your best option within a week.
It is damn hard work to find the right people and understanding the Chinese midset can be a huge benefit but if you do set out like I say you will start to get how they think within the first week.
Ken