Normally no tipping anywhere, and I am very anti-tip. That being said though, during my most recent trip to Beijing, I got the awkward pause twice from hotel bellhops and I broke under pressure. The weird part of this for me is that I am of Chinese descent but grew up in North America (used to tipping), so most Chinese people don't know that I am not a local and thus shouldn't be assuming that I would tip them. Even then I got the "there you are sir... umm..." pause twice. This had never happened to me before, anywhere in China. So I'm not sure if maybe hotel bellhops have become so accustomed to being tipped that they are surprised when they are not.

Also, as I did tip twice this is what I tipped:

First time, I actually had no cash left on me after the taxi to the hotel and I opened my wallet and told the bellhop "oh I'm so sorry, I don't have any cash left", even after this he just said "oh..." and didn't make any motion of leaving, and actually looked at my wife who was across the room. Finally I awkwardly asked her for some cash and tipped him 20 RMB (normally I would give $2-$5 per bag and I had 4 bags, but this guy pissed me off so I took the smallest bill she had). FYI: this was Doubletree Beijing

Second time was a bit better in the sense that the guy was actually cheerful and nice, but this time I wanted to test the system and so I made sure he didn't lift a single piece of luggage. He literally just pushed the cart from elevator to room. Yet he still gave me the awkward tip pause, but since he was nice I still tipped him 50 RMB (about $10 for walking from the elevator, I put bags onto the cart, and took all of them off and into the room). This was at the Hilton Beijing Capital Airport.

I had lived full time in China for 7 years, and usually visit around twice a year now, and have never gotten this awkward pause before (not at any Western hotels either) so I was very surprised to get it twice in one trip, especially since no one would guess I wasn't a local if I didn't say so.

So I don't suggest tipping as the service should not be directly correlated to tipping as it is unfortunately in North America. But at the same time, it seems bellhops have suddenly gotten used to being tipped. The first guy I gave 20 RMB to actually sounded disappointed by the "small" tip and he actually said "oh, ok （哦，那好吧）" when I gave it to him. Therefore even though I am firmly anti-tip, I still break under the pressure to do so and just wanted to warn you that all of a sudden there is some pressure for it in China. For restaurants though, NO TIPS. Any place where tips are expected will have a fixed service charge that is worked in to your bill anyways, and the only places where I have seen people tipping (aside from Western hotels now) is during live stage shows.
As for who to tip at the hotels, I wouldn't have had tipped anyone, but only the bellhops were actually waiting for it.