I teach 12th Grade American Government and Economics.
I convey important information or bulletin announcements. Then teach lessons: I try to grab their attention with a great visual or interesting discussion question so that they are interested from the start, give a brief lecture to introduce the concept, and then reinforce their learning with an engaging project or activity. I grade assignments, communicate with colleagues and parents, plan lessons. Meetings: department, committees, etc. Attend school events. Coach (when sport is in season).
While you are in college, you may want to look into being an instructional aide or an AVID tutor, or in an afterschool program. Anything at a school site that may help you determine what "a day in the life" is like, or what part of the education field you would like to be involved in. Also, to gain experience - something to put on the ol' resume.
Here's the first step for college students
Try to complete some observation hours or job shadow a favorite teacher that you may have had in the past. It is very useful for picking up effective teaching techniques, as well as helping you to determine if teaching is actually something that you truly want to do. I know a lot of educators who feel that teaching is not a profession or a career, it's a lifestyle.
"You should get another credential...history teachers are a dime a dozen."