I have never been to China but we import from there and my business partner has spent a lot of time there. These are some of the things I've picked up from him and others.
Generally, I'd take whatever you would take on a first trip to a large US city plus the stuff that you feel helps you in a foreign country like a phrase book, consulate contact info and so on.

We do all our voice communication to and from China using Skype. Some of the neater ways you can use Skype are not available for China but it still may be worth investigating for your trip. Also, I believe most Chinese cell phones don't have voice mail. Everyone texts instead. From what I recall, most Chinese use their cell phones almost exclusively for texting.

This may sound a little geeky but all of your electronic communication in, to and from China can be monitored by Chinese intelligence. During the Olympics, I recall seeing a security expert on TV saying that all US visitors, when not using their cell phone, should remove the battery. Even when off, it will be remotely turned on and used as a listening device. He was a security expert so perhaps he was more than a little paranoid or just more likely to be of interest. Their interest in you will depend on who you are and what you are doing there.

I don't know where or why (business, pleasure) you are going but around the coast (Shanghai, Guanghzou, Shenzen etc.,) you will find it extremely urbanized and very modern. Some of these cities are bigger and much more modern than New York. I wouldn't worry that much about food poisoning unless you are going to a wedding. Still, I'd take the Imodium. From what I've read when doing research on importing some food products (and consequently food poisoning in China), I would never eat at a Chinese wedding. Of course, I wouldn't drink the milk either.... From everything I've heard, Chinese food is generally very very good and of course very different from the Americanized Chinese food you get here.

Finally, when I find myself coming up out of strange NY subway stations or really any strange train station, I rarely know which way is which and if I'm walking somewhere from the station, I find it helps to have a small compass just to orient the map and the brain.