Systematic searching involves a number of steps, and we devote a page to each of these, as follows:

• Develop a search strategy
• Consider text mining and search filters (if you're doing a full review)
• Decide where to search, and run searches
• Document your search strategy
• Review and update your search.

Searching is a critical part of conducting the systematic review as it provides the evidence base for your research. If you are doing a full systematic review, your search strategy needs to be:

• Comprehensive and unbiased. You need to search across a number of databases and grey literature sources, and consider hand-searching bibliographies and key journals.
• Clear and reproducible. You need to document the search terms you are using, how you combine them, and where and when you have searched, so that others can evaluate and update your review.

Yale University Library has some useful videos about systematically searching the literature: Systematic Searches.