Some things that might be helpful during your trip to China could be:
A dictionary,
The address and phonenumber of the hotel/hostel you will be staying at,
Medcine against food poising (also see the Health + Safety section for more information)
In summer: a scarf even when it’s warm because of the airconditioning,
Mosquito repellend;
In winter in the north for ice festivals or even Beijing: really warm clothes and shoes,
Very important! Leave half of the suitcase empty especially if you are a woman, because you will do sooo much shopping and you won’t know where to put the things. Men also leave space: All the women will love you when you come home with wonderful presents and you’ll find a lot for your self too! ;)