There are two broad, general directions in which to write your literature review: The "top-down" search and the "bottom-up" search

The "top-down" search begins with actual references from academic and scientific journals, in other words. The strategy assumes that you already have a high level of familiarity with the research area and the issues and knowledge that relate directly and indirectly to the area. As such, "top-down" searches tend to be less systematic than "bottom-up" searches, and for a novice researcher, the omitted source material can translate into important missing information.  The "bottom-up" method is strongly suggested for those who are new to the process of investigating a research question. It is the more effective strategy when one is still trying to build a general knowledge base in the field of interest, and it is the one that I will recommend that you choose as a novice health sciences researcher. It will allow you to become more familiar with broad concepts that you are just now mastering in other courses, and how these essential concepts related to current issues and ongoing areas of debate and uncertainty. 

STEPS INVOLVED IN A BASIC "BOTTOM-UP" LITERATURE REVIEW

• Try to list all possible terms that might be useful "index terms" in checking broad references and databases regarding your area of research interest. Use a glosssery to assist you in covering all possible relevant terms.

• Look up your topic and terms related to it in a good general reference. Read each entry carefully and make note of the key terms and books/articles included in the bibliography.

• Use the index terms and information from the general reference to do either a Computerized Literature Search or a Manual Search of the Literature (or both, if the resources are available.)

• Skim the abstracts, tables of contents and outlines of the articles and books you initially select in order to determine which will be most directly relevant, informative and helpful to you in understanding your topic and refining your research question.

• Obtain actual electronic or print copies of the references that appear to fit the above-stated criteria, select the best from among them, and begin outlining and note-taking.

It is not at all unusual for the process of reviewing the literature to cause you to consider changing your research question. In my experience, novice researchers usually start with an overly broad question, and end up refining, focusing and working to a more specific and testable research problem.