Coverage - Does it cover the topic broadly or is it narrowly focused?
Audience - Is it written for academics, professionals, or the general public? Is it easy to understand or does it use a lot of highly technical and/or specialized terms?
Bias - Is the information presented objectively (unbiased) or from a particular point of view (biased)? Does it support or contradict your own arguments on the topic? Understanding opposing viewpoints can help you to strengthen your own argument so don't ignore them.
Relevance - How does the source relate to your overall topic? How do you anticipate using it in your research?
For articles you can read the abstract to get an idea of what it's about or if there's time, read it in its entirety.
For books take a look at the table of contents, view relevant chapters, author credentials, etc.