The main difference between Chinese and western eating habits is that unlike the West, where everyone has their own plate of food, in China the dishes are placed on the table and everybody shares. If you are being treated by a Chinese host, be prepared for a ton of food. Chinese are very proud of their culture of cuisine and will do their best to show their hospitality.
Sometimes the Chinese host use their chopsticks to put food in your bowl or plate. This is a sign of politeness. The appropriate thing to do would be to eat the whatever-it-is and say how yummy it is. If you feel uncomfortable with this, you can just say a polite thank you and leave the food there.
Don't stick your chopsticks upright in the rice bowl. Instead, lay them on your dish. The reason for this is that when somebody dies, the shrine to them contains a bowl of sand or rice with two sticks of incense stuck upright in it. So if you stick your chopsticks in the rice bowl, it looks like this shrine and is equivalent to wishing death upon a person at the table!
Don't tap on your bowl with your chopsticks. Beggars tap on their bowls, so this is not polite. Also, when the food is coming too slow in a restaurant, people will tap their bowls. If you are in someone's home, it is like insulting the cook.
Make sure the spout of the teapot is not facing anyone. It is impolite to set the teapot down where the spout is facing towards somebody. The spout should always be directed to where nobody is sitting, usually just outward from the table.