Once you have chosen a 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.
If my topic is about the environment and sea level rise, here are some questions I might ask.
WHAT questions focus on a particular aspect of the topic: What is sea-level rise?
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 is the sea level rising?
WHEN questions focus on timing or history. When did sea levels start to rise?
WHERE questions focus the topic on a location, either geographical or other. Where is sea level rise an issue?
HOW questions focus aspects of the topic, on a process, or on the origin. How can sea level rise be stopped or slowed down? How can people help?
WOULD / COULD questions focus on possibilities. Would recycling more help prevent sea level rise?
SHOULD questions focus on the appropriateness of a particular action, policy, procedure, or decision. Should the government do more to help with sea level rise issues?