Travel documents : chances are, you need a Business Visa. You will need an invitation letter from the company or branch located in China. Check the website of your local Chinese Embassy for more details.
Money : always keep cash with you, most hotels and big shops accept Master Cards / VISA / AMEX, but others don't.
You can easily take cash from most ATMs, personally, I had more luck with VISA than Mastercard (less common in Asia).
Phone / Data plan : its cheap, you can buy a SIM card anywhere (I recommend China Unicom, they have better 3G coverage, at least in Beijing). Then you can buy 50 or 100 RMB charge as you need, on the go.
In case of emergency, there are at least 2 international hospitals you can count on :
They are quite expensive, compared to other local hospitals, but its high quality.
Things to pack :
- tissues (you never know if the local restrooms will have some or
- some basic meds for stomach aches
- Lots of business cards (Its very important to share them with your chinese co-workers / clients)