Make sure that you've had all the common vaccinations; check into your measles and tetanus vaccinations, which may be due for a booster.
The CDC recommends getting the Hepatitis A and Hepatitis B shots if you'll be traveling to China. Both of these require a series of shots over a period of time, so it's best to start at least a few months before your trip.
If you're traveling into rural areas, typhoid and Japanese encephalitis may be concerns.
If you plan to spend a lot of time outdoors or be in contact with animals, a series of rabies shots may be prudent.
If you're traveling to rural areas, malaria may be a concern---ask your health care provider to give you a prescription for antimalarial drugs (atovaquone/proguanil, doxycycline, chloroquine or mefloquine) to take on the trip. You may want to bring along a supply of your favorite anti-diarrheal, pain relief, antihistamine and other common medications so you can be as comfortable as possible if you develop an illness while you're traveling.
