Use AND to connect words that must appear in a document. This *narrows* your search.
horse OR equine
Use OR if only one word must appear in a document. This *broadens* your search.
equestrian*
Use an asterisk to truncate a word and allow for different endings, for example, equestrians, equestrianism, etc. (But be careful if there are words with the same beginning that are unrelated)
"feral horse"
Use quotation marks to enclose a phrase or words that must appear together in a document. You can combine quotation marks with AND or OR in a search: "feral horse" OR "wild horse"
horse NOT crazy
Use NOT to exclude words or terms from a search. If you're looking for articles on horses, articles about Chief Crazy Horse are probably not going to be relevant.
Library Guides -- and Subject Guides in particular -- can help you choose databases that are relevant to a specific disciplinary approach. There is a Subject Guide that corresponds with each Whitman major. General Guides offer information about certain kinds of sources, such as government documents or primary sources.
The advanced search interface lets you be more specific in your Google search: search within specific domains, for results with specific licenses, in specific languages, etc.