Should you leave the section about previous employment on a job application blank if you've never worked before?

Not necessarily. If the reason you've never had a job is because you were in school, then in that section you could put that you've just recently graduated, with a degree in .... etc., and include your GPA (if your grades were good), and you can also include any other academic achievements. If you've never been employed because you were a homemaker and raising a family, then you could put some info about that in that section of the aplication. Being a homemaker and raising a family requires a lot of time, energy, work, organizational skills, accounting (managing a family budget), etc., to keep a home running smoothly. Use what skills, knowledge and experience that life has given you to put something in that section, and be sure to write it in a manner that reflects a positive, intelligent, and quick-to-learn attitude.