Read widely and deeply from a wide range of materials. This includes not only the books in the field you want to master, but also articles from the most respected, peer-reviewed scholarly journals in your field of study. Because you will have to take a comprehensive examination that tests your mastery of your field of study, outline or summarize the materials you read. Make notes of the central themes, arguments, theories and research findings. Keep these summaries in a notebook for study as you prepare for examinations.
Seize opportunities to conduct your own research. Get an assignment as a research assistant to a tenured faculty member, which will enable you to take part in that professor's research work. In addition, write your own papers for presentation at academic conferences or for submission to journals. A paper you wrote for a class can be the basis for a conference or journal paper.
Join a national or regional scholars association that is related to your field of study. Many of them have discounted student membership rates. Membership allows you to receive the association's journal(s). Associations also hold conferences at which papers are presented. Academic conferences provide an opportunity to present your own work for review and critique. They also offer excellent networking opportunities.
Interact with faculty members and fellow doctoral students in your Ph.D. program. Rarely does one master a field of knowledge by being a loner. Interaction with professors and fellow students affords more learning opportunities outside the classroom. Forming a study group with other students, for example, allows all of you to help each other as you prepare for class tests or comprehensive exams.
Work closely with your dissertation adviser and follow her advice to the letter. This person will supervise your research efforts as you prepare your dissertation. Whenever you meet with your adviser, be prepared and have specific questions. A good working relationship with your adviser is a key element to a successful dissertation of original research.