Use your research statement or question to identify keywords.
Topic statement: "I think some video games like Call of Duty advertise violence to sell the brand."
Keywords: video games Call of Duty advertise violence
Keywords can include similar words or opposites. Try to think of some alternate words or use a thesaurus to help.
(image generated from Thesaurus.com)
Keywords can also include words that more broadly or narrowly define your topic. It can be helpful to create a picture of how concepts or words relate to each other by drawing lines between the keywords or grouping them together. This picture or concept map can be changed or added to as research continues and more about the topic is learned.