A dissertation proposal is the first draft of a book proposal. It is also, of course a proposal more generally. (You should collect successful examples of proposals while in graduate school).
We don’t usually theorize what we want in a dissertation proposal, though. Here is one department’s official text. This is good, but it could be more helpful.
So let me say this:
What goes into a good dissertation proposal?
It should be no more than 20 pages.
It should be densely footnoted (10 point, single spaced) – because you need to demonstrate that you know the literature. And that you understand which fields are in play.
It should say something about the scholarly intervention you are making. This can be long, or it can be short, but it should be very direct.
It should begin with a story, a vignette, a close reading of something. This is fundamental. It should be brilliantly written. And it should demonstrate the methods you’ll be using in the dissertation itself.
It should include, up front, a prospective table of contents, and, at the back, a bibliography of primary sources.
It should have a title that would make sense to a reader of the New Yorker.
It should include, within the prose, a description of the contents of each chapter, and the contribution each chapter makes to the entire project. After reading the proposal, you should be able to understand, as a reader, why the chapters are in a particular order.
I am not a fan of subheadings, and I would never ask you for them, but you should know that many others kinds of proposals will ask you to break out the sections of scholarly significance, methods, etc.
Importantly, the proposal should make a big claim for why this project matters, why it will move a field or fields to change the way we study a big topic, why we should read it.
And there should be a timetable – a roadmap to completion, no matter how tentative.
People say – and I even say – “write a book not a dissertation.” But you can’t do the former without at least understanding how to do the latter. And, in truth, they aren’t that different. So try this: write everything for a broad audience. Write it well, that is. Care about your prose.
Because, until the dissertation is done, this proposal is likely to be a calling card for you. You’ll be asked to share it, and you should generally be ready to do so.