Many students will go on to graduate school where research proposals usually precede the writing of most papers. The graduate student should expect to write a proposal for nearly every course. A Master Thesis or Doctoral Dissertation will certainly call for a research proposal. Frequently, sociologists find employment in agencies which undertake research projects, such as the federal government or Gallop agency. Not every proposal will be the same.
Some instructors have different requirements than others.
Likewise, some agencies have different guidelines. Nevertheless, every good research proposal has some basic elements. You should have a section which clearly states what the research problem or objective is and why it is relevant. All good research papers take account of what other authors and researchers have contributed to our understanding of the topic at hand. Thus, you should try to achieve as complete a review of the existing literature as time permits.