If you search a catalog or database and receive a large number of results, add a limit or additional keyword in order to retrieve a manageable and relevant number of results to review. At the same time overly narrow search terms can return too few results. One way of solving both problems is to use Boolean operators (AND, OR, NOT), which allow you to limit or expand searches depending on your needs.
For example, a search for presidency AND leadership will return items that contain both concepts":
leadership OR decision making returns items that contain either one of the concepts or both:
united states NOT latin america returns items that talk about the United States of America but do not mention Latin America:
Phrase searching:
An important strategy to use when searching for phrases ("decision making") or titles:
For example, "Strategic President Persuasion and Opportunity"
will search for those words in that order, finding the 2012 book:
Strategic President: Persuasion and Opportunity in Presidential Leadership
Truncation and Wildcards:
Most catalogs and databases enable users to search variations of keywords by using truncation (*) or wildcard (e.g., ?, $, !) symbols.
For example, one could search for politic* to find poltic, politics, political, politicking, and so on.
Wildcard searches are for differences within words: a search for wom?n will return results for woman, women, and womyn.
Nested Searching:
When pairing two or more keywords with another keyword, it is important to "nest" the former terms within a larger Boolean search.
presiden* AND (leader* OR (success OR successful OR "decision mak*")) AND "united states" will return results for the union of the three subject areas 
Results include: Eshbaugh-Soha, Matthew, and Jeffrey S. Peake. Breaking Through the Noise: Presidential Leadership, Public Opinion, and the News Media. Stanford University Press, 2011.