For typical things like taxi, hotel or meals, I'd say you don't need to tip as it's not really the norm in China.
However, if you're working with tour guides or people who interact with foreigners often, they might be accustomed to the tipping practice - and might even expect it. It might be helpful to try and use your best judgment when it comes to tipping - of course, you never really have to tip, but I say it wouldn't hurt if the service was really exceptional.