The Goldilocks approach: Not too broad, not too narrow, but juuust right.
The 5 W's approach: Narrow your topic by thinking about Who, What, When, Where, and Why.
The Advanced Search approach: Searches with one term answer "what is...?" type questions. Searches with at least two terms answer more complex questions that you can take a position on.
The 1-minute approach: You have a good working knowledge of your topic when you can talk for an entire minute without stopping.
Depending on your topic and your knowledge about it, you may want to find an overview. An overview can help you narrow your topic, put it in context within its discipline and identify "classic" research. Use the sources below to start or ask a librarian for help.
In-depth reports of current and controversial issues of the day.
Reference books by Oxford University Press, including the Oxford Digital Reference Shelf.
Online reference works from a variety of publishers.
Not sure if it's okay to use Wikipedia or a web search as a starting point for your research? Check with your instructor or a librarian!
For an overview of the issue, check out Wikipedia's Citing Wikipedia article!