Referring to another message:
It's not recommended nor usual for a girl from Europe or the Americas to try to join directly an agency in Asia and especially in China. The usual way is to let her mother agency handle that, it's also less risky especially as there are many new "agencies" in China we don't know anything about. Further once back home only an agency will be able to handle all those problems related to payments and other paperwork. There are also further good reasons to have a good mother agency,
For open calls just keep it simple. Basic clothing, no prints nor obvious logos, just plain basic colors. It's also important that the clothes show well the form of the body.
Avoid flashy colors. Black and white are not ideal for shooting polaroids, due contrast problems it can be hard to see the form of the body but it depends on the lighting conditions, the camera and the person who takes the snapshots. A neutral grey or so is probably better.
No or, if you insist, only a very basic light makeup. Bring some scrunchies to tie your hair up as well as heels. Bring or wear a simple plain swimsuit.
Don't lie about your age, stats etc. as you'll be measured anyway. Also bring an official ID.
Don't worry, just be yourself. Listen and answer questions but there's no need for long explanations.
Blunier