An important early step is to become familiar with the overall topic of interest. You'll get a sense of what is known on the subject and various subtopics. Follow your interests and decide on a specific focus for your research.
Explore your topic by using encyclopedias, scanning books, looking at headlines in the news and popular media, and by skimming journal titles and abstracts.
Write down the terms, symbols, people, events, or categories used to describe your topic and your (ever more) specific focus. These words (and their synonyms) will help you to find additional information sources.