Keywords are going to be the terms you will use to search for information. Just typing in your entire topic sentence is not an efficient way to search. Here are some tips for using keywords effectively.
If you are looking for editorials or opinions articles on a topic, include the format in your keywords
Keywords: global warming, editorial
Condense your topic down to the 3 or 4 essential terms.
Example Topic: "Nirvana, Pearl Jam, and other bands introduced Grunge music to popular audiences and changed rock music in the late 80s early 90s."
Keywords: Nirvana, Pearl Jam, Grunge, popular music
Consider synonyms or alternate words to describe your term
Example: "England used Privateers in the New World in order to harass Spain without committing official navy vessels."
Keywords: England, Great Britain, British, Privateers, Pirates, New World, Caribbean, Atlantic
Keep track of the terms and indicate which ones are most successful. This will help you when you go from search in one type of resources to another.