Customs
...at the airport
If you travel using long distance buses, train or fly within China you will always be required to put your luggage through a scanner. Every station will have a bustling security zone. This includes metro/subway.
On entering China you will have to fill in a digital landing card. This is a new system that is intended to replace the physical cards that are available on arrival at all airports. You'll then pass a temperature check (ensure you don't have a fever at the time of arriving). There will be a scan check. The items prohibited can be checked online but basically use common sense. Avoid long knives, subversive literature and so on. You may be asked questions by the immigration officer who'll stamp your passport.
IMPORTANT: Never overstay your visa in China. You will incur daily fines and face the risk of never being allowed to re-enter China again.
Departing through an airport
If travelling both internationally and domestically, you are not allowed to carry sharp objects, any liquids at all (including unopened wine or bottles of water) and lighters. You must dispose of these at the airport security area in the bins provided. This includes carry on baggage and checked in luggage. If a lighter is found inside your checked in luggage it'd be pulled aside and you'll need to locate and remove it. This will time up valuable time!
Just recently, they also do not allow power banks through security unless they have been certified as safe. These banks are usually demarked with a 'CCC' logo (China Compulsory Certification - 3C) and will be checked separately at security. If your power bank doesn't not comply, it will be removed. You will not get this back.
If you check the pictures on this page, including one of China's biggest airlines, for the requirements, it'll help you avoid loss, embarrassment and even a penalty at any of China's impressive but quite strict airports.
