A research proposal sets out what you intend to achieve and how you will go about it. Lots of information about writing a research proposal can be found here. The requirements of research proposals differ depending on the question you want to address. Research projects aiming at finding generalized knowledge (empirical research projects) should at least include (although not necessarily in this order):
An important starting point is to explain the real-world significance of the topic and the project. You must show that there is a particular question or problem related to this topic that deserves to be studied. Do not start a research proposal with a lengthy discussion of the context. Mention the problem or question you want to tackle in the first section. Explain context and reasons for studying the topic later. This helps the reader and the writer to focus. It is very unlikely that you are the first to study this topic, so refer to the most relevant literature in the introduction. This summarizes what has previously been done. Put as much of the literature review as you can in the research proposal. Not just in the introduction, which should not be too long, but also later in the theory and the methods sections.
After discussing the general problem and the knowledge already available, refine the topic into a clearly formulated research question (and some sub-questions, if that helps clarifying the research objective)). Mention explicitly the type of question you want to answer (see section on research questions). Sometimes it is useful to refine the research question further after a short review of the theories you intend to use.
In this section, you should discuss the existing models, concepts and/or theories relevant to the topic, and say how these will inform your work. If the question is descriptive, the least you need is a clear conceptualization of the most relevant concepts. If the question is explanatory, just mentioning the relevant concepts is not enough, you will need the most relevant elements of the theory.
In this section you describe how you will go about answering your research question. Why is this approach suitable for answering the research question?
How will you select your cases? If you select many cases what sampling technique is used? If you select only a few cases or one case, how did you select that case?
In this section you should describe the data that will be used in your study, why these data are appropriate for testing the theories you have discussed, and how they will be collected. What type of data will you be using (e.g. quantitative or qualitative?). You may be collecting original data, or using an existing dataset.
On what basis will you draw causal inference, e.g. statistical inference using regression analysis, study of critical/extreme case.
You must think about how long the project will take and what resources it will involve. The project must of course be feasible in terms of time and money. Be realistic about this! Give a provisional schedule for the completion of the various parts of the project, (such as data collection) and the anticipated date of completion of the project as a whole.
Although you may have mentioned this in the introduction, it is good to pay attention to this topic in a broader sense. For example, in the introduction you may have stated that we still do not know why people vote in elections. In a part on the scientific and social relevance you may stress the importance of participation for the stability of democracy.
Think about how you will structure the final report, and provide a provisional table of contents in line with this.
Not all bachelor- or master projects aim at generating generalized knowledge. Projects addressing applied questions like predictive questions, remedy questions and design questions, for example, apply the findings of existing research to address a particular problem (see section on research questions). In this case, it may not be possible or necessary to discuss research design, or case selection, for example. However, it will be necessary to have a more extensive literature review and a more extensive theoretical section, since you have to explicate which theory or theories you will apply. Since applying theories also involves measuring variables you will probably need sections about data collection and data analysis too.