Primary Sources, or What can you Trust?

Back when I was doing a history major I learned about who to trust.  For history, the best sources are those written at the time, and even better, by participants.  These are called "primary sources" and are valued above "secondary sources"  histories written long afterward.  For instance, Winston Churchill wrote "The Second World War" (six volumes)  shortly after WWII ended.  This makes Churchill a primary source on WWII.  Whereas Rick Atkinson's fine "Army at Dawn",  copyright 2002, is a secondary source.  In cases of conflict between primary and secondary sources,  greater weight is accorded the primary source, on the theory that people who were there at the time are more likely to get it right.
   This sort of thinking can readily be applied to internet sources.  Putting stuff on the internet is so cheap anyone can do it.  No one approves internet postings, and you can find internet postings that support literally anything.  Some very good information is published on the net, and a whole lot of really awful stuff is too.  How to tell the good stuff from the awful stuff?  If you can't tell, the internet can feed you that awful stuff.
   Check for an author.  If there is no named author, (anonymous) that's a down check right there.  It means the author feared retaliation if his name became known.  If the author is some one you have heard of or know something about, that's an up check.  Does the writer have his facts straight?  You aren't an expert in his field, so you cannot judge everything, but there is always the little stuff, that you do know.  Dates, names, places, does the writer get them right?  If the small stuff is in error, it casts doubt upon everything else.  Does the writer support his main thesis with concrete examples, real experiments, real historical examples, surveys, photographs, things with time and date and place and names?  Or does the author engage in handwaving?  Has the author written other stuff?  Google ought to find it for you, even if it's obscure.  Do other writers comment upon your author?  If no one mentions your author, one way or another, that means they all thought he was not worth a comment.