At a bare minimum, Cochrane guidelines expect a systematic review to search in: Pubmed/Medline, EMBASE, and the Cochrane Library. Below are links to those resources and others that you might want to consider. Depending on your topic, you may need to use resources outside of the typical biomedical databases. For a listing of all available databases you can check our web site at http://hsl.med.nyu.edu/databases or you can Ask the Library for a consultation on selecting appropriate databases.
To learn more about PubMed search, see the library's guide to searching PubMed.