Once you have identified your list of keywords and synonyms hold on to that list. That same terminology can be used when you are writing your paper so that you can vary up your sentences and not use the same words over and over.
Also, remember to try those different combinations of keyword searches in a variety of places. Pick two different databases or if you have tried the library catalog then go in to the ebook database and also search there. Great research usually doesn't happen in one search or in one single place.
To expand searches in order to get more targeted results
To encourage multiple searches that build off of an original research question
Watch the following video on conducting keyword searches in Google vs. The library catalog vs. The Databases