There are a number of ways in which these aims can be achieved, and it will be helpful for you to have a clear idea early on of the type of dissertation you are going to produce.
The most common type of dissertation is the empirical research project. Here, the overall goal is to try to answer one or more clearly specified research questions by collecting and analysing empirical (i.e. factual) evidence. The evidence used to answer the question(s) might be primary evidence (i.e. material collected yourself, using such methods as interviews, questionnaire surveys and observation), or secondary evidence (i.e. gained from existing sources such as official statistics or government reports), or a combination of both.
While the empirical research project is the most common type, other forms of sustained rigorous investigation can provide the basis for a dissertation. For example:
A conceptual or theoretical study. The overall goal here is to explore in depth one or more key ideas, concepts or arguments, in order to clarify them, assess their validity, or tease out their implications. A study of this kind would include a meticulous and systematic analysis of certain key sources (academic texts, research reports, official documents, etc.) in which the ideas and concepts have been used or examined. It would also be likely to involve a more creative element, in which an attempt is made to develop a new way of conceptualising (i.e. thinking about) the issue in question.
A design-based or problem-based study. The overall goal here is to explore ideas, and advance knowledge, through the process of working on a design to solve a problem or meet a brief. The problem or brief will usually relate to a specific context, which could be at any of a number of scales (e.g. a particular site, or a whole sub-region). The investigation would be likely to include such elements as: describing the design context and the design problem; examining current theory or best practice ideas for dealing with the problem; generating alternative solutions in outline terms and assessing them against stated criteria; working up a solution in more detail; and evaluating the developed solution so as to be able to reflect on, and take forward, the theories and best practice ideas examined earlier in the process.
Since the investigative process you adopt, and the shape of the dissertation you finally produce, will depend on the type of dissertation you are doing, you need to think very carefully in the early stages about what track you are going down. The possibilities, and their implications, need to be discussed with your dissertation supervisor.
Source: University of the West of England