One of the most common questions we get here regards exchanging money. Chinese money (the yuan renminbi or RMB) isn't freely exchangeable....it isn't always readily available outside of China (although this is changing), and it certainly can't be used to pay bills or add to your savings back home. On the other hand, most Chinese businesses and government offices aren't set up to take foreign money.
So how does one change money here?
The OFFICIAL route is to exchange money at a bank, usually the dreaded Bank of China. All too often, the process gets turned into a long and horrendous bureaucratic ordeal. You'll need to bring your passport, visa/residence permit, work permit, etc. with you. You'll get a so-so rate at the bank. You'll also pay a pretty stiff tax unless you have a Work Permit/Foreign Expert Certificate explicitly stating that you can convert a certain amount of money tax-free. This permission comes from your employer and must bear their official seal.
The BEST RATE comes from exchanging money through the black market by using what we call a "currency exchange consultant". It's recommended that you get at least an introduction through a local friend; don't wade into this one on your own. Most of these guys are pros, but there is always a tiny chance of being burned or busted. Be discreet. Get a money-checking light (a small black light), widely available at very low cost, and learn the ways to manually check Chinese money, posted in English in many banks. In the overwhelming majority of cases you'll get your money changed in about 2 minutes, no ID required, with no problems and at a better rate. In many cases someone at your employer can handle money exchanges for you; by all means check it out.
If I were not a responsible webmaster person, I would add that only newbies and terminal pinheads (and perhaps the chronically lucky) ever change money at a bank the nice safe legal way. But I am, and so I won't.
You will often see shadowy figures lurking outside of banks, offering to exchange money. It is recommended that you NOT use them; if you must then try to get a Chinese friend to do it for you. When you work with someone you don't know, or have a mutual friend with, you run a greater chance of getting counterfeit bills or being assessed a punitive exchange rate because you are foreign.
You can also buy RMB at many hotels with a passport and visa. This is fairly quick and convenient, but it's expensive...you'll usually get a pretty lousy rate this way. You also can't turn your RMB back in for your foreign currency. They'll send you to the bank for that.
Similarly. international airports will also generally have areas where you can exchange money. Rates here can be the worst, but this varies from place to place.
If you have an internationally-accepted credit card or debit card, such as Visa, Mastercard, or JCB, you can withdraw RMB from an international-enabled ATM. God knows what kind of rate you will get. Most ATMs are NOT international-enabled, but most cities have at least a few that are. If you get stuck, try the ATMs in 5-star hotels and upscale shopping areas. To my knowledge it is not possible to draw foreign currency from an ATM anywhere in China.