Use the operator AND to find only sources that include both keywords. This search will bring back fewer results than searching either keyword on its own.
Use the OR operator to expand your search with additional keywords. This will find sources that include either word, so you'll see more results than by searching for just one keyword.
Use “QUOTES” around your search phrases. This will bring back results that only use that exact phrase.
Additionally, if you are retrieving results that are closely associated with your search phrases, but not relevant to your topic, then you can use the NOT operator to exclude these phrases from your search.