Keep in mind these are the requirements to teach LEGALLY in China. Many recruiters will hide these requirements from you and trick you into working illegally. For more info and details, please see http://reddit.com/r/chinatefl and http://reddit.com/r/chinateachers. Take note that there is NO MANDATORY REQUIREMENT TO HAVE A TEFL CERTIFICATE.
It is also interesting to note that unless you have a post-graduate degree, foreign English teachers are no longer considered to be “experts” in China.