Out of necessity due to both lack of cabs and lack of money, this year I have been using Beijing city buses and have been finding them quite a useful transport method when the subway doesn't go where I want to go, or when i just don't feel like being a gopher and heading underground. Have also used them on in other cities, even when I wasn't quite sure where I'd be ending up. (The hotel receptionist or concierge can advise visitors.)

Remember that it's not necessary to figure out the entire bus system. You only have to figure out the most critical routes from where you are living/staying, and where you most often like or want to go.

Even though subject to rush hour snarls as any other vehicle, at least when the empty taxis have all vanished, or refuse to pick you up, a bus will usually be coming by within 10-15 minutes and can at least get you closer to your destination (and out of the cold!). And for RMB 1 (or 0.4 with a Yikatong transport card for bus-subway), one of the best deals going in Beijing!