About Chinese Names

Chinese people using first name and surname, but when they call somebody they start from the surname and then the first time.

I wish to know that crucial information before I met my current wife as at the beginning for a half year, I call her by surname.

From my experience, it is sporadic that Chinese people call each other by the first name. It happens only between friends or when you speak to children.

Another trivia I heard but I didn’t find the source yet is there are only around 400 surnames in use in China.