You normally need a bachelor’s degree, ideally related to your teaching subject, and teacher training such as a Post Graduate Certificate in Education or a Master’s in Education, which is suited to the age range you are applying to teach.  A TEFL certificate alone is not sufficient. You will need a recent criminal record check as well.  Many schools also require that you have teaching experience. Finally, there is an age limit to get a visa in Qatar for a teacher, so you must be younger than 50.