In Hong Kong and Macau tipping has become the custom, but not to U.S. levels, yet. Restaurants will routinely add a 10% service fee, although I hear that this fee does not necessarily go to the front-line staff. While the waiters will say the requisite 10% is all that is expected, there is still always a line for an additional tip. In observing others, I tend to think the actual custom is to pay a little more than the 10%, rounding up to the next appropriate bill size, averaging about 12% to 13%. Paying exactly 10% would be like paying exactly 15% in the U.S., the bare minimum you can get away without causing any ill-will.
Anybody handling your luggage should get at least HK$ 10 to 20, depending on how far they had to schlep your bags around. Tipping taxi drivers is not expected. If I had a ride that cost HK$ 19, and I gave them a twenty dollar bill, they would actually offer the $1 change, which I waved off. Personally I think you should tip cab drivers just a few extra dollars, or just round up to the next convenient bill size.
In mainland China you will hear very emphatically that tipping is not expected. However, based on three previous trips there, that really isn't the case if you are white and/or speak English. When I Chinese person pays in a restaurant or receives any kind of service one would tip for in the U.S., they don't tip, and nobody says anything. However, if I don't, I never get off so easily. I remember vividly at a restaurant in Shanghai the waitress brought me the check and waited for me to put money in the money holder. I happened to have exactly the right change so I put it in, and she just stood there with the folder open, waiting for me to put more in. When I did, she left.
All things considered, the expense of tipping is a lot less here than the U.S., so think about what you are saving, rather than spending on tips.
That is the end of my crash course on Macau. Please choose one of the menu items on the left, or go back to any of the previous sections.