How did you become interested in this field? Establish that you have had a long-term interest in the field and that you have taken positive steps in pursuing your interest. Give the committee members a sense of your particular talents and abilities and their relevance to your academic interests.
What experiences have contributed toward your preparation for further study in this field? Demonstrate your interest by providing examples of research experiences, internships, work experience, community service, publications, or life experiences. Briefly describe what you did in each experience. Also, make sure to articulate what you have learned about the field and how those lessons stimulated you to pursue an advanced degree.
What are your future goals? Specifically state your degree objective (Master's or Ph.D.) and specify what subdisciplines you are interested in pursuing. For example, if you are applying in political science, the committee needs to know whether you are pursuing American Politics, Comparative Politics, International Relations, or Political Theory. Let the reader know that you are planning a future career as a university professor, researcher, or consultant, or in public service or private practice (or whatever your goal happens to be).
What are your research interests? Within your subdiscipline, you should be able to identify one or two topics that are of interest to you. When possible, be specific about your research agenda. Remember that you will be working with professors in research; therefore, your research interests should parallel those of the faculty. (You will usually not be expected to know exactly what you want to research; faculty know that initial interests often change.)
How are you a "match" for the program to which you are applying? Explain what attracts you most to the institution/program to which you are applying. Align your research interests with those of one or more of the affiliated professors. The better the "match" with the program/professors, the better the chance that you will be admitted.
Other factors to weave in (remember these are secondary factors):
Give examples of personal attributes or qualities that would help you complete graduate study successfully.
Describe your determination to achieve your goals, your initiative and ability to develop ideas, and your ability to work independently.
Describe background characteristics that may have placed you at an educational disadvantage (English language learner, family economic history, lack of educational opportunity, disability, etc.).
Leave the reader believing that you are prepared for advanced academic work and will be successful in graduate school.