Systematic reviews attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. Systematic reviews follow a defined protocol and include a reproducible search methodology, conducted in multiple databases. Retrieved citations are reviewed by multiple people and compared to a predefined inclusion/exclusion criteria. It is not unusual for a systematic review to take 18-24 months to conduct.
If this is the type of review you are interested in conducting, this guide will get you started but contact your Subject Librarian for help with your search.
People often use the term "systematic review" when they really mean a thorough literature search, that covers multiple databases. This guide will also help you conduct a thorough search.