Is there enough information for the source to be helpful?
Is the information it includes detailed enough, or is it too general?
Professors often complain to us that their students are using sources that are tangential to their topic at best. Before you read a source, before you even print or download a source, make sure it's highly relevant to your project. How? Look at the subject headings and abstract for journal and magazine articles. Look at the headline and lead paragraph for newspaper articles. For books, look at the table of contents and index.
For whom is the source written? The general public? An academic audience? Highly advanced experts in the field?
Is it too technical for you to understand? Is it too elementary for for scholarly research?