Tipping is not an established practice in China. You’re not expected to tip anyone, including taxi drivers, waiters/waitresses, or hair stylists. In higher end restaurants in Hong Kong (and increasingly in Shanghai and Beijing), you might see a 10% service charge added to your bill.
Having said that, the practice has been catching on (enthusiastically I might add) — the expectation of getting a tip has increased in tourist services that cater to foreigners. For example, it’s a good idea to leave a tip (or group tip) to your tour leader (depending, of course, on the number of days and quality of service). But don’t feel as if you’re obligated to do so (especially if the service was sub-par or mediocre) — domestic Chinese (and most Asian) tourists typically don’t tip anyone while in China.
Also, bell hops in upscale hotels that see a lot of foreigners are more than happy to get a small tip (again, don’t feel at all obligated to do so).
[ Side rant: Personally, the practice tipping in hotels has always seemed unfair to me. Why is it that the maids, reception, and kitchen staff rarely get tipped….but the bellhop expects a nice tip for wheeling my luggage (which has wheels) into an elevator? Or worse, the doorman who expects a tip after spending all of 10 seconds whistling a taxi over and moving my bag 5 feet into the trunk? ]