Need to Have a Precise Topic
It is essential that one defines a research topic very carefully. For example, it should not be too far-reaching. The following is much too broad:
"Life and Times of Sigmund Freud"
However, this is more focused and specific and, accordingly, a more appropriate topic:
"An Analysis of the Relationship of Freud and Jung in the International Psychoanalytic Association, 1910-1914"
Limitations of Study
In specifying precisely one's research topic, one is also specifying appropriate limitations on the research. Limiting, for example, by time, personnel, gender, age, location, nationality etc. results in a more focused and meaningful topic.
Scope of the Literature Review
It is also important to determine the precise scope of the literature review. For example,
In evaluating studies, timeliness is more significant for some subjects than others.
Scientists generally need more recent material.
However, currency is often less of a factor for scholars in arts/humanities. Research published in 1920 about Plato's philosophy might be more relevant than recent studies.