Photography in China
China is a constant photo opportunity. People everywhere doing interesting things. Landscapes of all varieties. Its pretty rare anyone will tell you not to take a picture.
What to Bring
Normal travel in China covers a wide range of situations. For the casual photographer your favorite camera will do. Bring lots of extra memory cards, however you can buy them if you really run out. Ordinary batteries are also available here but the quality might not be as good. If you have a laptop then you can backup your photos as you go.
For the more serious photographer, either a digital SLR or a 4x3 system with interchangeable lenses is suitable. Personally for digital SLR I use a Canon body (1Ds Mark II) and carry a 16-35L, a 35-70L and a 70-200L IS. I also have an Olympus Pen-P2 which takes beautiful pictures. I have a flash for both. I always shoot RAW or RAW and JPG as this gives lots of options on the computer.
Buying Camera Equipment in China
You can buy memory cards and obtain plug adapters or extension cords which act as adapters quite easily. There is a photography market on the west side of Beijing which has pretty much anything you might have forgotten. But don't expect it to be cheaper than the west, especially for cameras and lenses. If you need some extra hard disk space you can buy portable drives easily. Memory cards and other accessories are often name brand fakes. As you'll likely be busy best to come prepared.
The Great Wall
The wall is best shot early in the morning when the weather is right. End of the day light can also be good. Even in fog you can still get some spectacular shots. Black and white can work well too if its not sunny. If you really want to get good images of the wall I'd recommend spending the night sleeping on the great wall, that way you wake up and can get the first rays of the sun. There are also hotels at various sections of the wall, but you'd have to wake up early and walk quite a distance to get to the right location.
Tibet offers some wonderful photo opportunities. Be aware many of the temples will charge you a fee to take pictures or video. Sometimes its low, other times very high. Do not take pictures of Chinese soldiers or you will invite trouble.