Decide why you want to attend graduate school, and what you hope to do with your degree. If you are thinking of pursuing an MA, do you hope to continue on to a PhD? Do you hope to work in a museum or archive, or teach at the High School level?
Decide what basic area you would like to focus on in your studies. Generally, people come to a graduate program with some sense of where their interests are, geographically, thematically and temporally. You do not need to have a topic for a thesis or dissertation in mind, but you should be able to say something such as: “I am interested in the daily lives of factory workers in Ohio in the mid-20th century” or "I would like to research Thai nationalism in the twentieth century" or “I would like to work on tactics of woman suffragists in the progressive era”. These interests are not set in stone, and our graduate students often find that their interests change by the time they begin to write their thesis, but they will give you and us a sense of whether our program is likely a good fit for your interests.