What are good majors to take to become an elementary teacher?
You'd definitely want to major in "Elementary Education" - most colleges offer this specific major. If you're not totally sure that's what you want to do, you can also pick a more general major.
I know all the homeroom teachers in my school all have their specialties. It allows them to have full planning experience the all of course have Elementary Ed. degrees with specialties ranging from Science to Social Studies, to literacy, and Math. They divide planning into what their specialties are and in some cases they swap classes to teach only their specialty to both 6th grades for instance.
The ideal is you get an undergraduate degree in Pedagogy with a specialization in early grades. Throughout the course, you will have the opportunity to perform an internship that will give you experience and pedagogical practice in the area. You can also search for voluntary activities in the area of school reinforcement for children.
You can choose to major in Education or you can major in anything else and go through Alternative Teacher Certification program. I was a Business and Computer major in college, but later went through the Alt route to become a certified teacher.