Is this going to be your first time living and working abroad?
Are you going to be in beijing / Shanghai, or somewhere (comparatively) smaller?
I think that you should prepare yourself for some of the cultural differences. I thought my first school in Argentina was terrible, but looking back now, it just didn't fit into what I was expecting.
I suggest typing 'how to avoid culture shock' into a search engine. Many of the tips you'll find are part and parcel of what people have said here. Learn a bit of the language. Reading this forum, and posting on it once you're here, will definitely help.
It's possible that your expectations of how good a teacher you need to be may be far higher than your schools, and standing on a pedestal trying to pull people up can be soul-killing. Far better to come in with low expectations, and then raise them if necessary.
As long as you've researched your school properly and swopped emails with current teachers, you should be fine. It's easy to get teaching resources here, apart from reference books, so if you have a copy of David Riddell's 'Teaching English as a Foreign Language', 'English Grammar in Use' (Raymond Murphy) or 'Practical English usage' (Michael Swan), bring them along. I've never seen them in schools, and Chinese equivalents are riddled with mistakes.