Consider a Source's Role in Your Research
For some papers it may be appropriate to cite an article in a popular magazine, and for others it may be necessary to cite the research findings published in the scholarly journal on which the magazine article was based. So, why use one source over another?
You must consider what role the source will play in your paper. Ask yourself, is the information it contains useful for your purposes as a writer? Does the source contain strong quotations or hard facts that would be effective in your final paper? Is it relevant, in terms of the subject matter and in the way it tackles it?
Remember, what you're looking for is the best possible sources for your particular paper. Ask yourself not only "Will this do?" but "Will something else be better?"
Consider, as well, how using this source in your paper will affect the future direction of your research. Does it contain information that challenges your assumptions about the topic? Does it present any strong evidence against your position that you must then counter or refute with opposing evidence?
Does it suggest a new direction that might be more interesting? Your research project will probably grow and change as you learn more about it. It's wise to check in with yourself now and again to make sure you have a clear direction and if it's the same as you began with, or completely new.
Finally, consider whether a source is directly relevant to your research question. It's surprisingly easy to get sidetracked by a persuasive book, article, or Web site on a topic that is only slightly connected to the direction of your research.