A proposal is often the first 1/3 of a project report, with the main
sections of:
Introduction
Background and Related Work
Methodology
Timeline
References
Heilmeier's Catechism
In general, a good proposal should be able to answer Heilmeier's
Catechism (credit George
Heilmeier). To paraphrase:
Problem statement: What are you trying to do? Articulate your
objectives without jargon.
State of the art: How is it done today, and what are the limits of
current practice?
Novelty in approach: What's new in your approach and why do you
think it will be successful?
Impact: Who cares? If you're successful, what difference will it
make?
Cost/Benefit: What are the risks and the payoffs? How much will it
cost? How long will it take?
Milestones: What are the midterm and final "exams" to check for
success?
Note, some/most of these will be addressed in the proposal, but will
probably not be in the above exact order.
Approach
Generally, outline the proposal - basically, provide sections and
subsections with bullets for content and order for each. When ready to
write, see the individual "one-pagers" for each section.