Authority & Credibility - Who specifically wrote the source, or who is responsible for publishing it? Why should you care what they say? How do they describe themselves? And more importantly, what do others think about their credibility?
It’s usually more important who is responsible for publishing the information, rather than the individual author. If the writer isn't in the employ of whoever published it, then you will see a brief biography.
How can you find out the reputation of the magazine, newspaper, or organization that published the information? Google the name to see what others are saying. If it is a real news organization, there will be a Wikipedia entry on it.
A very useful tool for a thorough evaluation of news organizations and major think tanks is NewsGuard. See Adding NewsGuard to Web Searches for more info.
Evidence - What is the evidence? Is it complete, or does it have holes in it? Is it balanced, or overly biased or slanted?
Some sources will be relevant and useful, but do not give the reader a complete picture of the issue and ramifications, such as an editorial that is slanted to a particular perspective. But just because a source is not balanced does not mean it would not be useful. It just means you need to find sources with other viewpoints as well.
How does the information compare to others? Similar, or an outlier?
This you won't be able to judge until you've read several sources...
NewsGuard thoroughly evaluates over 8,000 online news sites. Use Microsoft Edge browser and download the extension for free. (Otherwise it's a subscription service, $4.95/month.) Use it on laptops. (NewsGuard claims it will work on the app version on mobile devices, but it isn't in the settings for Apple iOS.)
Adding NewsGuard to Microsoft Edge
Within Microsoft Edge, click on Microsoft Edge in the toolbar, then Microsoft Edge Extensions. Search newsguard and click to add it.
When you click the Get button, it prompts you to create an account in NewsGuard. Click the Sign In button, top right corner, and either create an account or sign in with an existing Apple, Facebook, or Google account.
Once you've created a Newsguard account, it appears to want a credit card for the subscription. Ignore that, scroll down to the bottom, and it says Not ready yet? Maybe later. Click the Maybe later link, and it will add the extension.
Once you have NewsGuard installed, you'll see a green, gray, or red icon next to the results list in Google, or at the top next to the URL when you are on a site that NewsGuard has evaluated. Hover over the icon to bring up a short evaluation of how well it follows journalistic standards. Click on See the full Nutrition Label to view a detailed analysis, with references.