Living in Asia you quickly adjust to its customs. This is my second stay in Beijing, and the second time I visit its markets. These are my guidelines:

First off, make up your mind about the maximum price you are willing to pay for the item(s) that caught your eye. This may sound easy enough, but it is considerably more difficult to do so with sellers swarming around you trying to sweet-talk, stress or intimidate you into making a quick (or even unintentional) buy.

Ask for the marketers "best price". Shake your head at said price (always, ofcourse, with a smile on your face). Explain that you are aware of the pricing tactics in the markets, claim to live in Asia or something similar, and then ask for their "Chinese prices".

Frequently they then will tell you to name your own price. A simple rule is to start out with 1/10 of their initial "best" price and then work upwards with small increments. If they still decline when you are beginning to close in on your maximum price, thank them politely for their time and slowly begin strolling away towards the next stall (neighbouring stalls usually carry the same or similar items). If they don't call you back after a couple of steps your bid probably really was to low and you can try again at the next place, now with a slightly higher bid.

Some examples (1 CNY is almost 1 SEK, also remember that it always is cheaper to buy in bulk):

Prices per item, in CNY, with a range reflecting the quality of the piece,

T-shirts, blouses & tank tops: 40-60.
Boxers & panties: 5-10.
Shoes: 100-200.
Watches: 200-250.
Passport holders: 60-120.

Popular "brands" include: Diesel, Gucci, Calvin Klein, Dolce & Gabbana, Tag Heuer and Breitling.

Finally, some no-no's:

Don't be cheap; a couple of extra CNY's really isn't that much to argue about (unless you want to make a point to a fierce seller).

Don't lose your temper; even if a discussion over a price gets heated and the marketers intrude your personal space (this is a common tactic in order to intimidate you).

Don't stroll to far into the stalls; many sellers invite you in and then block the way out with their (and their co-workers) persons making it difficult for you to use the "then I'll see what the next stall has to offer" routine.

Shop 'till you drop,

-Prepp