Consider a literature review as a typical research publication presenting a study, its results, and the salient points scholars can infer from the study. The only significant difference with a literature review treats existing literature as the research data to collect and analyze. From that analysis, a literature review can suggest new inquiries to pursue.
Identify a focus
Similar to a typical study, a literature review should have a research question or questions that analysis can answer. This sort of inquiry typically targets a particular phenomenon, population, or even research method to examine how different studies have looked at the same thing differently. A literature review, then, should center the literature collection around that focus.
Collect and analyze the literature
With a focus in mind, a researcher can collect studies that provide relevant information for that focus. They can then analyze the collected studies by finding and identifying patterns or themes that occur frequently. This analysis allows the researcher to point out what the field has frequently explored or, on the other hand, overlooked.
Suggest implications
The literature review allows the researcher to argue a particular point through the evidence provided by the analysis. For example, suppose the analysis makes it apparent that the published research on people's sleep patterns has not adequately explored the connection between sleep and a particular factor (e.g., television-watching habits, indoor air quality). In that case, the researcher can argue that further study can address this research gap.