Obtain your undergraduate education. You will need to have a bachelor's degree before you can go on to pursue a Ph.D., but you do not necessarily have to pursue your doctorate in the same field you obtain your undergraduate degree. However, you should pursue a doctorate in a field related to your undergraduate studies in order to avoid having to take additional prerequisite coursework. A master's degree is not absolutely necessary to obtain a Ph.D; some Ph.D. programs allow you to obtain the master's degree en route the doctorate.
Research your field of intended study. If possible, you should pursue a Ph.D. in a field that you are extremely passionate about. This will make it easier for you to put in long hours of study without getting bored. You can conduct simple research by reading papers already provided by the U.S. Bureau of Labor Statistics. The bureau's website will provide you with information regarding the job market outlook, earning potential and additional training and licensing for your field, if necessary.
Conduct research on scholars in your field of study as well. Find scholars whose research interests correspond with yours. If these scholars are still working and are doing so at a college or university in the United States, these may be the schools to which you need to apply.
Submit your application to the graduate programs with scholars whose interests correspond to yours. When you submit your application, you will most likely have to submit a statement of intention. This statement should highlight your research interests and the reason why you think the school is a good fit for you. The admissions committee will want to know how your work will contribute to the scholarly community as a whole. Many schools' graduate programs build their reputation on the work of both their faculty members and graduate students.
Complete your Ph.D. coursework. Most Ph.D. programs require you to attend seminars and some lecture courses during the first two to three years of study. These are designed to provide you with the knowledge foundation you need to pass your comprehensive examinations.
Prepare to take your comprehensive exams. Most Ph.D. programs require you to pass a series of written and possibly oral exams in order to qualify for the degree. These exams can ask you any question about any aspect of your field of study, so you will need to be widely read and highly knowledgeable of all of the research in your field.
Write and defend your dissertation. You will have to submit a proposal to your Ph.D. committee and have it approved before you can complete your dissertation. Once your dissertation has been completed, you will be required to defend your thesis in front of your dissertation committee and possibly the rest of your department.