Forget any semblance of good manners - get those elbows out, brothers and sisters, and be prepared to push, jostle and even shoulder charge. Otherwise you risk not making it on to any public transport, to the front of any queues, or even getting fed at a café. It's not rude, it's just the way it is.
If you don't have a smartphone, get one, and download the best Mandarin translation app you can find. The Chinese grasp of English is tenuous, and that phone will be your lifeline, especially in taxis.
If you're travelling internally on Spring Airlines, don't bother taking a book - halfway through your flight the stewards perform a very entertaining exercise routine that all passengers dutifully follow, sort of like armchair aerobics. Only in China.
Carry your passport everywhere - we couldn't even rent bicycles in Shanghai without surrendering our passports: nothing else except a bucketload of cash would satisfy the rigid man at the rental joint that we weren't going to make off with his crappy mountain bikes.
If you leave the main cities, make sure you have a good supply of anything medical or cosmetic you're likely to need. Otherwise, even if you miraculously stumble across a "chemist" or "pharmacy" in search of bug repellent or moisturiser, you'll end up with a toenail cleansing tonic or a paste that will ensure your virility for the next 100 years. Or something.
Finally, if you're in Shanghai looking for a mind-blowing tourist activity, take the Bund Sightseeing Tour. The sign promises a "high tech showing consisting sound, light, cartoons, and videos, as if going through the earth and enjoying an amazing experience" and I can confirm it delivered on all of those things, especially the "amazing experience" part - as in, amazingly crazy.
You ride in little cable cars beneath the river through a tunnel illuminated with loony light patterns while a booming voice shouts at you in English and Chinese and clowns loom from the darkness. Willy Wonka's psychedelic chocolate river tunnel springs to mind, just less terrifying. At the end of the three-minute journey you'll ponder one simple question: why? So good we did it twice.