To get the most out of searching in databases, it is best to search systematically. The Systematic searching: pharmacy and pharmaceutical sciences tutorial will guide you through this process, and demonstrates how to build a search in Ovid Medline.
Building a search in CINAHL (database)
Watch this short video on how to search using CINAHL Plus produced by MNHS Subject Librarians (3.56 minutes). You can apply the same principles to search in other databases.