There are no general rules. Here are some rough guidelines:

Some characters are used almost exclusively for one sex. For example, almost any character containing 女 will generally only be found in women's names. 

Names that reference flowers, birds or beauty are more likely to be women's names. Names that sound grandiose are more likely to be men's names. 

However, in Chinese there are no formal rules about names, and any family can name their child whatever they like, even if the name does not match the child's gender. So there is no definitive way to identify a person's gender from their name -- not even for Chinese people themselves.