How will you know if what you find is a good resource?
First, the source must be valid, reliable and accurate. (Although a quick wiki search could lead you to a good source, it will not be acceptable as a resource.)
Sources should be associated with an academic institution or reliable organization (such as CNN, the Library of Congress, The New York Times etc. ...). If you are unsure of the source, validate it as a resource by comparing it to other sources in a variety of formats.
Lastly, don't forget to look beyond "print" texts (digital or hard copy). Research sources such as podcasts and videos can be great resources.
Resources for Research:
Mrs. Juster's Virtual Classroom: Literary Periods
LHS's Library Media Center: Databases
Research Tools (including help with Noodletools)