Before you can search for studies related to your research question, you need to know where to look. So, spend some time identifying the databases and other sources that might have the information you need.
At the Center for Evidence Synthesis in Health, we’re interested in research related to medical or health questions, so our go-to databases come from the world of medicine. If your systematic review is about a different academic discipline, you can probably name the major databases in your field. If not, a librarian can help you find them.