Once you have selected an initial topic, the next step is to develop research questions. You'll do this by using probing questions, such as what, why, when, how, would/could, should.
Phrasing your topic in the form of questions helps direct the research process.
WHAT questions focus on a particular aspect of the topic: What are the long-term effects of traumatic brain injury?
WHY questions ask for an explanation of something--why something happened, why it did not happen, or why one thing is better than another. For instance, why do some people with traumatic brain injury develop post concussion syndrome, while others do not?
WHEN questions focus on timing or history. When did the NFL acknowledge that playing football is linked to traumatic brain injury? When did awareness of traumatic brain injury begin?
WHERE questions focus the topic on a location, either geographical or other. Where, or in which particular sports, are traumatic brain injuries most prevalent?
HOW questions focus aspects of the topic, on a process, or on the origin. How do traumatic brain injuries affect someone in the long-term? How do traumatic brain injuries affect someone in the short-term?
WOULD / COULD questions focus on possibilities. Could football helmet design decrease the incidence of traumatic brain injuries?
SHOULD questions focus on the appropriateness of a particular action, policy, procedure, or decision. Should the government regulate how the NFL responds to concussions?
Source: Mike Palmquest. Bedford Researcher. Colorado State University.
A good research question will lead to your thesis statement.
For example, the question...
What are the long-term effects of traumatic brain injury?
...might lead to the following thesis:
"Long-term effects of traumatic brain injury may include thinking and cognitive deficits, visual-motor disturbances, depression, suicide, progressive dementia and Parkinsonism."
Strong thesis statements
or "why should I care?" test
Source: Thesis Statements. George Mason University.