Finding reliable suppliers in China

Due diligence. This basically means that as it is your money that is going to be lost if you make a bad deal, you need to be responsible for any decisions that you make.
I think that the biggest mistake most new traders make is that they get online, hook up with a few suppliers, find some that can communicate in English and offer what seem to be pretty good prices, and then throw all of their money at the supplier. I doubt that these people would purchase this way back home and it surprises me that they are willing to do it here.
Nothing beats an actual visit to the suppliers factory to tie up all of the information that they have given you before you actually place an order. Flying all the way to China and back again can of course be expensive which is why 'China Helpers' can be a good idea. For a small fee they can act as your agent not an agent of the factory.