As you are searching for information and learning more about your topic, you will be refining the focus of your topic.You can start refining by answering the classic five Ws. (text version of infographic)

Infographic Text
Focus your Topic
The 5Ws
Who
a person, organization, demographic group (e.g., children)
What
an event, theory, discovery, product, or element
Where
a country, region, defined geographic space (e.g., Yellowstone National Park)
When
a time span, century, period of time (e.g., Victorian era)
Why
description of the significance of the this topic
Example
What: Social Media
Who: College Students
Why: Mental Health