Agree with the no tipping points.

There are cases where it's acceptable such as buying something from a street seller for more than the asking price. A little old lady was very grateful to me when I paid just 50p more than her asking price for a pair of flip-flops for my girlfriend - I guess that doesn't really constitute tipping.

I always find it hard not to tip in the restaurants (even as a Brit!) as I'm aware of their poor working and living conditions due to poor wages and long hours... life goes on and the little you can do is just be courteous and respectful. Offering water and food is absolutely fine and most Chinese will politely decline or accept if you do this discreetly.