As an ethnographer, you're concerned with studying a culture and writing about it. Your study may focus on human society and history (i.e., cultural anthropology) or might instead deal with a subset of society (for example, an institutional or business culture). Whatever the case, you will look at how culture and behavior are related, and conduct your research while living and/or working within the environment you study. This means you should have a plan for "blending in"; you should dress, communicate and engage in activities just as your subjects do. But first comes the research proposal.
Define what your study is and where it will happen. Explain your logic (i.e., why you will conduct your study this way and not that way) and include descriptions of how you will collect your data. Discuss the benefits of your proposed study and why it is important to you. Complete and include all of the necessary permission and release forms.
Organize your inquiry. Include research questions and try to answer them -- even if, at this point, you're making an educated guess. If you're studying village life, you may want to ask about hierarchy with regard to age and fitness or gender. If you plan to study the writing culture at a local company, you could ask how the presence or absence of resources or procedures affects written communication such as email and memos.
Create and describe your data collection plan. This section specifically describes what your research is and where you will engage in the study. Describe how you will conduct your research; do you have or need special access to the site? Blending in with the community you study is essential; there should be no plans to change anything in any way during the course of the study.
Mention authors and academics who inspire your study. It's critical to avoid doing the same research twice. Previous material published on your research subject -- academics call this "scholarship" -- will help you to frame your study.
Prepare for a variety of grading techniques. The nature of the ethnography varies, so don't get lost in the details. Instead, take into account any cues from your instructor. Some instructors focus on structure and methodology; others are more concerned with proposed benefits and discussion. Finally, ask yourself if your proposal is organized and easy to understand; make sure your plan is doable before you commit to it.