Put phrases in quotation marks: "hurricane katrina"
Use an asterisk for truncation (any ending of a term): communicat* will find communication, communicates, communicating, communicator, etc.
Many words may describe the same or related concept (movies, film, cinema, motion pictures)
To search for any one of a group of terms, use a capital "OR" and parentheses: (movies OR film OR cinema)
To search for all terms, use "AND": violence AND movies AND children
violence AND (movies OR film OR cinema OR "motion pictures") AND (children OR kids OR adolescents)
To be effective and thorough, go back and try searching multiple times with many different keywords