Boolean searching is built on a method of symbolic logic developed by George Boole, a 19th century English mathematician.

Boolean searches allow you to combine words and phrases using the words AND, OR, NOT (known as Boolean operators) to limit, broaden, or define your search. A good researcher should know how to do a Boolean Search.

"AND" logic

AND : Using AND narrows a search by combining terms.

"OR" logic

OR : Using OR broadens a search to include results that contain either of the words you're looking for.

"NOT" logic

NOT : Using NOT will narrow a search by exclusion. (Some search engines, like Google, recognize the minus (-) symbol, instead of the word NOT).

Quotations : Placing quotations around a specific phrase will help you narrow results in order to find information containing that exact wording.

Boolean Searching on the Internet
http://www.internettutorials.net/boolean.asp

Power Searching with Boolean
http://www.butterscotch.com/tutorial/Power-Searching-With-Boolean