What vaccinations do I need before coming to China?

The United States Center for Disease Control recommends that
before travelling to China for extended periods of time, you should
take the following precautions.  

Hepatitis A
Hepatitis B
Japanese Encephalitis
Rabies
Typhoid
Tetanus-Diphtheria Booster
Measles Booster

While staying in Beijing, it may not be so necessary to get the
Japanese Encephalitis or Typhoid shots, as it is more developed.  
However, if you plan to travel to less developed regions of China
during your stay, it may be a good idea.

For more information, visit the US CDC page.