Chinese customs are generally straightforward. Visitors to China must fill out a customs form upon arrival. When you enter the country you are asked to declare electrical goods and luxury items such as cameras, computer equipment etc. Keep this form until you exit to avoid paying duty on goods you brought into the country.
You may import 400 cigarettes, 2 liters of alcoholic beverages and 50g (2 ounces) of gold or silver. There are no restrictions on the amount of foreign currency you bring in to the country. You must, however, declare any cash exceeding US$5,000 or the equivalent. You may only bring in or out of China RMB6,000.
Prohibited imports include: fresh fruit, arms, ammunition, printed matter, films or tapes "detrimental to China's economy, culture and ethics", narcotic drugs, animals and plants.
If you purchase antiques in China, you must obtain a certificate of authenticity. You need this certificate to avoid trouble when departing. Present this form when going through customs to avoid having your antique declared a "cultural relic" and confiscated.