my boyfriend has a masters degree in history and at school he took things like history, geography and english. At university, he had to learn latin and french for his postgraduate study and he says its really worth learning another european language. Alot of his thesis was focused on eccelsiastic history so for that sort of thing, if your school offers religious studies that can be really helpful too.
In the U.S., most states simply need a bachelor's degree and teaching certification to teach. When you get to college, you go through the school of education and major in history. The individual college you go to will let you know what classes you need to take to graduate. It's not that complicated.