Who wrote or otherwise created the material? Is s/he an expert in the field? What are his or her credentials? Does s/he work for an organization? Is it reliable?
Are there any glaring factual errors? Grammatical or spelling errors?
B = Bias
People create materials for various reasons: to provide information, to push an opinion, to sell something, or just to be funny, to name a few. What is the purpose of this material, and does that tell you anything about possible bias? Does the author present a balanced point of view? Are there any obvious conflicts of interest? Is the tone objective, or is it emotional?
Recognize your own bias, too! Do you believe what you're seeing/hearing/reading simply because you want to? Because it fits in with your preconceived notions?
C = Currency, coverage, and credibility
How current is the material? What is an acceptable date range for your topic area?
Is coverage of the topic in depth, or is it shallow? Does information seem to be missing?
For research studies, is the methodology sound? What does that say about the credibility of the findings?
D = Documentation and duplication
Does the author cite his or her sources? Are they credible?
Can you find the same information in any other source? If you read it first on social media, can you also find it on the news or in a journal article? If research findings, have they been replicated?
Healthy skepticism is a good thing.
If you can't answer these questions, investigate!
You must determine what is appropriate for your topic area or assignment.