Typically completed in the fall of a doctoral student's fourth year, a dissertation proposal defense is required to proceed with the dissertation process. Each program has documentation detailing the requirements and process for doctoral students, which should be read closely and referred to throughout the process. Dissertation proposals are typically comprised of drafts of the first three chapters of the dissertation (Introduction, Literature Review, and Methodology).
Your thesis or dissertation work starts with identifying your broad areas of interest. From there, you'll need to learn more about the topics you're interested in so that you can narrow down from broad ideas to a focused research question.
As you're thinking about possible topics, consider:
Before you finalize your research topic, it is helpful to survey existing literature and use brainstorming techniques like mind maps to visualize your topic, make connections to evidence from existing scholarly literature, and generate new ideas.
For each broad topic you're interested in:
As you progress, you will need to narrow your research focus. The FINER criteria (Hulley et al, 2007) can help you evaluate your possible research questions. A good research question should be:
Feasible - The research question can be answered given the timeframe and resources available
Interesting - The research question is interesting to the researcher and the wider academic community
Novel - Answering the research question will provide new insights into a field of study or will extend, refute, or confirm existing findings.
Ethical - The research question can be addressed using ethical research methods which address necessary IRB / REB protocols.
Relevant - The research question is relevant to scholarly study and/or clinical practice.
Hulley, S., Cummings, S. and Browner, W. (2007). Designing Clinical Research. England: Lippincott Williams and Wilkins.