Connect your methods and your research together. Will they work together well or will they challenge each other?
What is the significance of your gap? How will it influence the topic and the reader?
If requested, provide a detailed schedule of research and deadlines.
Provide a properly formatted list of citations at the end.
And remember, a research proposal is largely hypothetical, so...
It will not trap you into one exact project. In the early stages, people commonly change their minds about big and small details.
Just try not to change your mind too far down the line. Focus on making this proposal as interesting to you as possible.
Sometimes it just informs your instructor or employer where you want to go with research. It proves initiative and thoughtful effort.
Your argument will change the most in the beginning of the process, so be prepared to revise and edit your proposal multiple times before submitting it for approval.