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 Japan AND literature will return items that contain both concepts:
poetry OR performance returns items that contain either one of the concepts or both:
Japan NOT China returns items that talk about Japan but do not mention China:
Phrase searching:
An important strategy to use when searching for phrases ("black and white") or titles:
For example, "The Diary of Lady Murasaki"
will search for those words in that order, finding the book The Diary of Lady Murasaki 
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 Japan* to find Japan and Japanese or politic* to find politician, political, politics, etc.
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.
Japan* AND history AND womyn AND Heian will return results for the union of the three subject areas
Results include: Objects of Discourse: Memoirs by Women of Heian Japan