The methodology section of the dissertation is likely the most independently difficult section to write. The academic focus of graduate school is overwhelmingly about methodology, which means that there is an excess of pressure placed on that section in particular by the superior scholars that will be evaluating the dissertation. In general, the goal of a methodology section is to explain what analytical tools are to be employed in the dissertation to answer the initial research question.
Review the methodology sections of other dissertations to acquire a basic template for what a methodology section should ultimately look and read like. Ask your dissertation supervisor to recommend a number of dissertations for you to read, thereby ensuring that your own methodology section does not stray too far away from what he or she is likely to accept.
Define the research topic of the dissertation as specifically as possible, fully developing the entire scope and purpose of the dissertation. A poor methodology section is often a reflection of a poorly thought out, incomplete, unspecific, or overly abstract research question. The methodology section demonstrates to your dissertation committee the instruments used to answer the research question. Thus, if the research question is unclear, then it will be impossible to judge the appropriateness of the methodology section.
Decide on the preferred methods to be employed to analyze the research question. For example, a sociological review of labor markets might include lots of interviews with managers and workers in order to establish the specific culture and context in which the labor market operates. By comparison, a statistical and economic analysis of labor markets might look at the impact of unemployment, wage levels, family size, and a number of other variables on overall economic growth. In short, the type of analysis you seek to employ (i.e. quantitative or qualitative) will drastically alter how the methodology section is written.
Outline your methodology section and discuss it with your dissertation chair and your dissertation committee before writing it in full. It is possible that you have a snag in your logic or methodology that you are unaware of that could drastically alter the outcome and even relative importance of your research.
Write the methodology section concisely, clearly and only with active sentences when possible. Concise and clear sentences are important to demonstrate to your dissertation chair that you have an unambiguous grasp of the methodology you seek to employ. The active sentences express that you have a clear direction and purpose.
Obtain the approval of your dissertation committee before you complete the study. If required, review and edit the methodology section a number of times over before continuing your dissertation.