Keywords are the most important words or phrases that describe your topic. For example, if your paper is based on the question, "Are we taking it too far by blaming fast food restaurants for obesity?" then your keywords could be: fast food and obesity. A search strategy in a database may look like this: "fast food" and obesity and (america or united states)
Most databases will allow you to search for phrases by placing the words in quotation marks. Example: A search for cost benefit analysis (without quotation marks) will you will get everything that mentions any of those words anywhere on the page. Searching for "cost benefit analysis" (with quotation marks) will make sure the whole phrase appears intact in the results.
A Boolean search combines keywords with operators (AND, NOT, and OR) to produce more relevant results when you are searching.
Some databases allow certain symbols to be used for searching multiple forms of a word. The Help section of each database will tell you if these symbols will work for seaches in their databases.
Plurals -- A plus sign (+) added to the end of a word instructs the database to search for singular and plural forms of a word. Example: holiday+ retrieves holiday or holidays
Truncation -- An asterisk (*) added to the end of a root word instructs the database to search for all forms of a word. Example: house* retrieves house, houses, households, etc.
Wildcards -- A wildcard is a symbol used to represent any character. The pound symbol (#) is often used as a wildcard. Example: wom#n retrieves woman or women