Select a database that matches your information needs. Consider the perspectives you hope to include, source type, disciplinary or interdisciplinary lens, and database functionality. Since each database contains a unique collection (with some overlap) you will likely use multiple databases before exhausting your search.
Google - good for taking a very wide view of a topic, using a variety of materials and "popular sources" not found in library databases (blogs, websites, news sources, reports, etc.) Domain searching can target your search results example, "climate change" + :.edu | :.org | :.gov.
Google Scholar - still a huge swath of information, but more focused on scholarly publications (including journal articles, book chapters, conference proceedings, etc.)
Web of Science, Scopus, and JSTOR - multidisciplinary academic databases with an explicit focus on scholarly publications, with many options for complex, targeted searching
Specialized databases - some are focused on a subject area (Sociological Abstracts, America: History and Life, etc.), while others are focused on a type of source (news, primary sources, images, videos, etc.)
Index of articles from scholarly journals spanning the sciences, social sciences, arts, and humanities. Provides cited reference searching capability.
The Web of Science “Core Collection” includes the following:
Arts & Humanities Citation Index (AHCI)
Book Citation Index - Science (BCKI-S)
Book Citation Index - Social Sciences & Humanities (BCKI-SSH)
Current Chemical Reactions (CCR-EXPANDED)
Emerging Sources Citation Index (ESCI)
Index Chemicus (IC)
Social Sciences Citation Index (SSCI)