Define the scope of your dissertation carefully, and make a careful and complete bibliography of the research project you're going to write about. Review the books and articles you've already read for your coursework, and look at what they cite. You should end up with about a hundred titles; if you have many more, your scope is too large, and many less, too narrow. As you produce this list you should notice what the seminal works are because these will be the most cited.
Focus on the seminal works you've identified, read them carefully and understand how subsequent research deals with the issues they raise. Use this past research as a jumping off point for your proposal.
Identify the conflicts, contradictions or gaps in the current scholarship that need to be addressed. Explain how your work will resolve the contradiction or fill the gap. Position yourself in relation to the seminal works you have identified. For example, David Hildebrand identifies a contradiction in the debate on pragmatism between Richard Rorty and Hilary Putnam. He asserts that his analysis will return to the works of seminal pragmatists such as John Dewey to show that current work misconstrues some of their points.
Write a succinct introductory section and use a small number of excerpts of quotes from the relevant sources to ground and explain your statements.
Summarize your proposed dissertation, chapter by chapter. The first chapter or two will expand on your description of your contribution to the field. You will probably deal more with secondary texts or sources. Subsequent chapters will focus more on primary sources of texts such as the works of an important philosopher or poet, or perhaps archival material if you are writing a history dissertation. This summary should not be more than five pages.
Include your bibliography. Divide the bibliography into categories based on your chapters, or other divisions that you feel are important to the subject.