In Guangzhou, and probably throughout China, tipping is becoming much more popular, especially when you see how hard some of these people work and for so little. Tipping frequently occurs when you are in a tour group, superior hotel, restaurant, train station and airport or somewhere else you can enjoy service.
If you are going to tip, tip in cash (don''t add it to the bill). Usually tip RMB10.00 for bellboys who carry one bag or RMB20.00 for many bags when you check in at a hotel. If you are uncertain about how much to give, just to tip based on your bill. For the tour guide and the driver, 5 - 10 US dollars a day per person is adequate.
But remember there is no need to tip; do so only if you like the service and want to.