Mathochist gave a pretty good overview of the process. I have done graduate studies in history, and several of my fellow students have gone on to finish their doctorates and look for work. (I also started in a California community college, so I really felt obliged to give add my two cents, having once been in your shoes.)
Be aware that research is an essential part of academic employment. The thing that really distinguishes university professors from high school teachers is the depth of knowledge in specific fields – that depth can only be acquired through original research. (No slight intended toward H.S. teachers, of course) You’ll find that, as a rule of thumb, the more highly regarded the school, the more pressure professors will have to research and publish.
Keep in mind that you are entering a very competitive field. Frankly, my friends have had a tough time getting teaching jobs in history. (We all went to a British university, and they have been trying to get jobs in American universities — it’s a very tough transition to make.)
Two essential things you can be doing right now: concentrate on getting good grades. If you can get into top grad schools, it is easier to get a job after graduating. A PhD from Berkeley is a hell of a lot better than one from a CSU – I can’t emphasize this enough.
The other thing is start doing concerted studies of languages relating to the historical topics you’re interested in. You’ll almost certainly be expected to have reading knowledge, if not fluency, in two languages before you are allowed to get your PhD. I would urge you to arm yourself with at least one difficult language, so long as its appropriate to what you wish to study. Anyone can learn French and German, but having German and Polish, or better yet, Serbo-Croatian and Russian, will make it easier for you to distinguish yourself in the field. (Of course, travel to these places will be essential to learning the languages well.)
Best of luck to you, and hope you persevere.
Or, as Bill said in the Sun Also Rises, “Never be daunted. Secret of my success – never been daunted.”