There are a few things that I would watch out for:
Don’t wear shoes inside someone else’s house.
Don’t put toilet paper in the toilet if there is a bin next to the toilet. The paper goes in the bin. Not an issue in hotels. (The pipes will get clogged)
Don’t do drugs or have a gun in China. If you are luck they will deport you. If you are unlucky you will go to jail.
Don’t tip unless you really really want to or if you are in a high end hotel/restaurant. They will generally run after you with the change and be confused.
Source: Quora