When should you question a sources credibility

If you want to be sure you get accurate information then its important that you use credible and unbias sources.

You should question a source's credibility prior to using it.

One should question: if the source is current (what is the date of the research), who is the author of the source (what authority/knowledge/experience do they have), what depth does the source reach, who is the audience, what is the purpose of the source, etc.