Begin with a basic idea of your topic then look for information to help you narrow down the topic, focus on specific concepts, and generate keywords for your searches. In this part of the process you're browsing and doing a little reading to get familiar with the topic and generate ideas.
You can start with a basic source like Wikipedia to get definitions and background info. Popular sources such as newspapers or magazines provide general information on current issues. Books are also helpful for background reading, even scanning the table of contents can help you learn about your topic.
Once you have some background information you can begin searching for scholarly articles to add depth to your description and analysis of your topic.