I've taken a few trips to China these past few years and have some favorites and tricks to share. This post is a work in progress.
Always get the business card of your hotel. The language is difficult and worst case you can just give your taxi driver the card to get you home.
China is a place where their food is so much better than it is in the states. Almost all Chinese food in the states is Cantonese, but there are so many other styles, some of my favorites include Hunan, Szechuan, Shanxi, and Yunnan. See a more complete list on Wikipedia
The great Chinese internet firewall blocks YouTube, Twitter, Facebook and randomly other things. The firefox plugin Cocoon is a nice way around it. So is Tor but it's a little slow. Be sure to download the list of bridges ahead of time.
Bring an unlocked GSM phone. A China Mobile card will run you $15 to have a number for a year.
Find places to go on MobileNative. You can browse in English and have your destination SMS'd to your phone in Chinese.
Beijing:
Best dumplings ever: Bao Yuan in Chaoyang
Fubar: speakeasy behind Stadium Dog
Middle 8th: amazing Yunnan food