OK, having been to China, and the Silk Market in Beijing less than a year ago, I can actually offer some info. The post above saying "offer 50%" and go up from there -
VERY BAD ADVICE - Rifleman must be related to a vendor.
That is far, far too high. To give you an idea, here are some of the prices we paid - high-quality Coach purses $9-15; North Face windbreakers - $12, Billabong t-shirts - $4, silk scarves - $4-6, soccer jerseys $7-9. Basically your first offer should be 1% of what they are asking. Don't be ashamed - their initial price is what you would pay for the real stuff here or even more. Always keep a smile on your face and be friendly - "ha, ha - you are crazy - way too high - I can give you $1" kind of stuff. If you are buying things like purses or watches - KNOW YOUR BRANDS - they will usually try to sell you cheap knock-offs, but if you tell them that you want real quality stuff, they will bring out the high-end merchandise. Mrs. Impaler got a couple Coach purses, and her Coach-expert friends can't tell any difference between the Chinese version and the real stuff. Be prepared to walk away - we got some of our deals as we were "leaving". Be prepared for some abuse - a few times I drove such a hard bargain, they would tell Mrs. Impaler to divorce me, not to have my children, and that I was a bad, cheap man.
That's when I knew I got a good deal. You should wind up paying no more than 10-30% of the original price, depending on the product.
Hope that helps.