The first thing to consider when looking at a possible source is how well it fits your needs. That, in turn, will be affected by the nature of your research project and the kind of information you are seeking.
Is it introductory? Introductory information is basic and elementary. It neither assumes nor requires prior knowledge about the topic. Introductory sources can be useful when you’re first learning about a subject. They are less useful when you’re drawing conclusions about a particular aspect of the subject.
Is it definitional? Definitional information provides some descriptive details about a subject. It might help you introduce a topic to others or clarify the focus of your investigation.
Is it analytical? Analytical information supplies and interprets data about origins, behaviors, differences, and uses. In most cases, it’s the kind of information that you want.
Is it comprehensive? The more detail, the better. Avoid unsubstantiated opinions and look instead for sources that consider the topic in depth and offer plenty of evidence to support their conclusions.
Is it current? You should usually give preference to recent sources, although older ones can sometimes be useful (i.e., primary sources for a historical topic or if the source is still cited by others in a field).
Can you conclude anything from it? Use the “So what?” test: How important is this information? Why does it matter to my project?