"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. The key characteristics of a systematic review are: a clearly defined question with inclusion & exclusion criteria; rigorous & systematic search of the literature; critical appraisal of included studies; data extraction and management; analysis & interpretation of results; and report for publication." -- Duke University Medical Center Library & Archives
A systematic review differs from a traditional literature review or narrative review, in that it aims to be as thorough and unbiased as possible, and also provides detailed information about how the studies were identified and why they were included.
Prior to starting your own research, you will want to look at existing systematic reviews - this is especially important so that you don't duplicate existing work. It can also be helpful to look at the approaches taken for systematic reviews similar to your own topic or discipline. You can find existing systematic reviews a number of ways:
Below are some books available at the Ryerson University Library & Archives discussing systematic reviews: