Generally 10 - 15% tips before taxes. One thing I found interesting here is we pay two taxes for "ready-to-eat" food, in BC where I come from, we only pay GST.
Regarding the service, it is okay. Most of time, the order comes very slow. It is better to have something in mind, so right after you sit down, you put down your order and then just wait for it.
Some dishes are good, and some are not. If you come from the north part of China, you might like it better, but if you are from South China, you might be a little bit disappointed.