Be sure to read and understand the assignment
Ask your instructor if you need clarification
What interests you and would make your assignment easier to tackle? You'll be devoting lots of time to completing the assignment, so it's important to make it less of a "chore" by choosing a topic that stimulates you.
Consider a topic that is suitable for the assignment and that will enable you to easily write the required length. If your topic is too broad, you may be finding too much information. If your topic is too narrow, you may not be finding enough information. Flexibility, in this sense, is essential, as you may need to change your topic once or twice.
Identify keywords (and synonyms) that relate to what you're researching.
If you're writing about leprosy in Hawaii, you could also search for the following:
Hawaii leprosy settlements
Hawaii Lepers 1860-1960
Father Damien in Hawaii
If you're struggling with the amount of information you're receiving (too much or too little) during the next few steps, you may need to consider refining your topic and starting over.