Who or what is the source? Who else can corroborate?
For any given claim or report, who is promoting it? Do they have a commercial or political interest in the validity of the claim? Are there ethical or professional standards of accountability that apply, such as within the legal, journalistic, academic, or public sectors, that would generally validate the credibility of the source?
The degree to which it is less clear who is making the claim or report, and why, the less credence is warranted.
What else has been published by this source? Does the body of work evince a commitment to truth, or to the interest of a particular group or point of view?
Is the claim or report subject to public scrutiny? Have conclusions, data, or positions been subject to rebuttal, refutation, or critique? Claims or reports made in a vacuum, not tested in the public sphere, warrant a skeptical response.
What facts, evidence, or circumstances would it take to disprove, effectively rebut, or refute the claim or report? Have these counterfactual scenarios been proposed and/or tested? What alternative sources are best qualified to posit a contrary point of view?
These habits of mind should inform any effort to ascertain or validate the credibility of any information critical to public discourse.