Make sure you buy a fanny pack for your wallet and passport. There is very little violent crime in China but pickpockets abound. I have known at least one person who had their passport stolen and she had to wait two weeks before the US Consulate could arrange a replacement for her. So be careful about this especially in crowded areas. Fanny Packs are the way to go. Check with your airline regarding luggage restrictions and take over a half-empty suitcase if you can. You will do a lot of shopping in China and will need the extra suitcase for your return trip home. Also make sure to take an adapter set with you. You may need to use your hair-dryer or recharge your digital camera. China uses 220v and there are several types of plugs in use in China so you should buy an adapter set instead of a single adapter.
Food & Water
The restaurants in the hotels can be quite good. But they are expensive. You will save a lot of money if you eat outside your hotel. The food can be just as good and you will experience the thrill of eating in a real Chinese restaurant. There are usually lots of restaurants around the hotels and these are recommended as they tend to be a little friendlier and may very well have menus in English, given their proximity to the hotels. But do yourself a favor and try to get out of the hotel to eat. The one exception is Breakfast. The Breakfast buffets in the western style hotels are wonderful and a great way to start your day in China.
The water is fine. Bottled water that is. But only drink the bottled water that you have bought in a drugstore chain or hotel kiosk. The reason ? There is fake bottled water in China too. And make sure not to complain about the water or food when you are in China. This will not sit well with locals.
Getting around by taxis is cheap. But trying to hail a taxi in a big city like Shanghai or Guangzhou can be a challenge. And even more so if you are a foreigner. Many cab drivers will not pick up foreigners because they know most foreigners cannot speak Chinese and you can easily spend an hour or two trying to hail a cab around rush hour. So choose a hotel that is near a subway or public transportation line or hire a guide to take you around.
Hire a guide
If you are going to China for the first time and will not be on a group tour then I would highly recommend trying to line up a guide beforehand. One way to do this might be to look on Craigslist for the city where you are headed to see if there are some students offering guide/interpreter services. A quick check of Craigslist Shanghai shows plenty. You may be able to interview some candidates on Skype and make a decision that way. Needless to say, you do not want to pay anyone anything before you have met them. You can also ask the Concierge where you are staying if they can recommend a guide. But finding a guide on your own on CL is probably much cheaper.
Keep your complaints to yourself
In China you will encounter a lot of situations that will make you shake your head. But at no time should you get angry or articulate your dissatisfaction to people. The one exception would be in the hotel where you are staying. In short, tell yourself not to be an Ugly American when you travel abroad.