Developing keywords from your research topic question is the first place to start before research. The video below will unpack how to do this task. You can use Bubbl.us to keep all your keywords including related terms and synonyms in one place. It also can help to visually see how terms are related to others. See the example below.
Truncation is used to shorten a keyword to its root-word level. It also finds all suffixes or endings of a word.
Use the asterisk:
Truncation symbol with this example will retrieve: history, histories, historic, historical, historian, etc.