A good proposal should consist of the first three chapters of the dissertation. It should begin with a statement of the problem/background information (typically Chapter I of the dissertation),

then move on to a review of the literature (Chapter 2),

and conclude with a defining of the research methodology (Chapter 3).

Of course, it should be written in a future tense since it is a proposal. To turn a good proposal into the first three chapters of the dissertation consists of changing the tense from future tense to past tense (from "This is what I would like to do" to "This is what I did") and making any changes based on the way you actually carried out the research when compared to how you proposed to do it.