Most etiquette writing about China makes it sound like a minefield. It is not. Six or seven habits cover almost every situation you will meet.

The single most useful concept is mianzi — face. It means: do not put someone in a position where they have to admit fault, ignorance or inability in front of others. Almost every “Chinese etiquette rule” is a special case of that one idea.
Business cards, gifts, a cup being refilled. Two hands signals respect and costs nothing.
Do not pocket it immediately. Read it for two seconds, then place it on the table beside you.
Not restaurants, not taxis, not hotel staff. It is not expected and can be awkward.
At a shared table, fill your neighbours’ cups first. Someone will do it for you; say 谢谢 and let them.
Especially at people, and especially at statues or religious objects.
A raised camera and a questioning gesture works. In temples, never photograph worshippers.
A raised voice makes the other person lose face and makes your problem harder to solve. Ask for a manager, stay flat, repeat the fact.
In a metro queue, people stand in a line. At a busy counter, a lift or a ticket window in a tourist site, the line may be a loose crowd and the operative rule is “whoever is most determined”. This is not rudeness; it is a different convention, and it applies less in Shanghai and Shenzhen than in smaller cities.
The practical response is to stand close to the person in front, hold your position, and not take it personally. If you are with a guide, they will handle it — this is one of the more underrated services they provide.
Fixed prices in shops, malls and chain stores. Open to negotiation in tourist markets, antique markets and anywhere the price is not displayed. The workable method: ask the price, look unimpressed, offer 40–50% of it, and be genuinely willing to walk away. Walking away is the entire mechanism.
Chopsticks — you can ask for a fork and nobody will think less of you. Slurping — fine, and in noodle shops it is normal. Blowing your nose at the table — avoid, step away. Public displays of affection — mild is fine in cities, more conservative outside them. Tattoos, piercings, bright hair — nobody cares in Shanghai, and curiosity elsewhere is friendly rather than hostile.
Chinese people will often change the subject when it comes up, or give a flat answer. That is not ignorance; it is caution in a context where the conversation may be repeated. Do not push, and do not read silence as agreement. The same applies to questions about Taiwan, Tibet and Xinjiang — you are a guest, and winning an argument is not the point of the trip.
Tell us your dates and what you actually want to see. A guide who lives there replies within 24 hours — with a plan and one clear total.