Generally speaking, Asia in general is a no-tipping zone; with Japan being a definitely no tip country, period. I’ve been told it’s offensive to tip in Japan as they will read a tip as meaning you need to improve service.
China is pretty straightforward too as there’s no tipping as well. Definitely no tipping in taxis or restaurants. Hotels I may offer a few RMB for the bellhop or housekeeper, but it’s certainly not expected.
Hong Kong is a bit of a mixed bag with its colonial western past and Chinese culture. Hong Kong I’d classify as no tipping, but tipping does exist. (Macau follows the same protocol as HK.)
If you take a taxi, don’t tip, accept all change. They’ll usually round up to the nearest HKD.
Nicer and more modern restaurants: Establishment will add 10% to the bill for a service charge. Do not tip above this.
No service charge restaurants: you can take all of the change and leave no tip, or leave some coins as a tip.
(As a side note, at fast food restaurants you do not need to clean up after yourself. Workers will bus the tray for you.)
Small tip to bellhop / housekeeping is appreciated, but not necessary. If you’re Chinese they probably won’t expect one, if you’re Western they might. Also depends on the level of hotel, if you’re staying at the Peninsula I’d suggest tipping. If you’re at the Best Western it may or may not be expected.
Hope these tips help next time you’re traveling. Feel free to comment if you have other thoughts on tipping. I’ve been here so long I forget to tip when I’m back in the U.S. which is terrible. At McDonalds I also forget to bus my own tray too.