Do your research. One of the first steps in haggling over a sale in Asia is to do proper research before making a purchase. It's easy to find out what the retail prices and market value prices of items are in Asia beforehand. For example, you can check out the listings on Yahoo! Auctions in Taiwan. I use Google Translate to get an idea what a page says.
Yahoo! is really big in Asia, bigger than eBay in my opinion. Almost everyone uses Yahoo! including Asian retailers and vendors. They aren't really used as auctions per se, but rather as an e-commerce site. These auction lists give you an idea of how much an item retails at different vendors. These prices are almost always lower than the retail price. I've bought cell phones, laptops and desktop computers this way. I just call up the retailers and get their location.
Bring a local. The best way to get a better deal is to go with a local friend or acquaintance. They will be able to haggle better and faster than you ever will. However, they do need to know a bit about what you want.
Find dead stock. Vendors have to sell a lot of volume in order to make a decent amount of profit. The trick is to find something that the vendor wants to sell quickly, like an older model laptop. Last year's models are a perfect example. Most vendors will try to get rid of their stock because customers are looking to buy new merchandise. They will be eager to negotiate.
Never accept the initial price. Let the vendor downclose himself on the item first before you start to haggle. This will give you a good start. The key technique is to be realistic. Never try and seriously underbid the market value of the item, otherwise you will just loose the deal. With a little to and fro, you should be able to get the price that you want.
Don't worry about your Cantonese, Mandarin or Japanese skills. In the end, haggling is just an exchange of numbers. You show your price, the vendor will show you his. Vendors are used to this and they use calculators and paper to convey their price. There isn't much talk involved. If you talk in English, your tone will convey your meaning in most instances.
Don't be afraid to walk away. Walking around and seeing other vendors for the same item will give you perspective on your deal. Returning to see the vendor half an hour later will give you the edge. Walking away from a sale isn't hard if the price is too high.
At the end of the day, you should never be afraid to leave the deal on the table if the price isn't right. I've had vendors come up to me, after a bout of haggling, and offer me the item a lot closer to my desired price than initially. --Range