Learn "bu yao" ("I don't want"; it's the closest equivalent to "No, thank you") and be prepared to say it a lot. Pretty much non-stop in any major city and even landmarks outside of cities.


If you're lucky, you'll be visiting places right after rain. It's the only time the smog lifts.


Almost all the outlets are 220V, even the ones with plugs from nations that have 110V. On the bright side, most camera chargers and related paraphernalia are multi voltage. I'd recommend bringing a small laptop (possibly a netbook) for purposes of checking email and uploading your photos -- the Internet cafes are numerous, but you don't know what's on those computers that might store your email/flickr/whatever password. (And I'm not talking about the government; just mischievous other users. You likely won't encounter any issues with the much-publicised-in-the-west Internet filtering unless you actively seek out controversial content.)


Be prepared for very personal questions from strangers wanting to exercise their English; but shy away from any opinions on Taiwan, Tibet, or any Tiananmen Square incidents (and don't seek theirs, either).


The generation born since the Cultural Revolution (1968 onward) is a lot less nationalistic than their parents, and certainly more open minded about potential change -- but it's still a relatively conservative place where you don't want to push any buttons. That said, it seems like more people there are always on the lookout for a good laugh -- it's easy to turn a mistake into a gag that crosses language barriers.


Re: photographing the military. There may be hesitance to be in photographs, but there's also not as much strict military doctrine grilled into the soldiers, the police, or the paramilitary police. If you hold up your camera and shrug, most of them will nod back whether it's ok or not -- they're not the stoic palace guards of the UK.


Above all: Have fun. It will be an awesome adventure.