Do not take materials which may be used for religious proselytizing. Christianity is officially recognized by the PRC, but you may not take in any religious materials beyond what it would be reasonable for you to use while there. Anything judged additional may be confiscated by customs. You could be delayed or denied entry. You could be fined.
Most Chinese hotels have hostesses on each floor.
These young women are partly there to help and partly to watch. Do NOT invite a Chinese resident to your hotel room. Avoid any sexual contact with Chinese residents. Absolutely do NOT exchange any currency except at sites and stations approved by our guides. Criminal penalties for possession, use, or trafficking in illegal drugs in China are more strict than you can possibly imagine.