Use the C.R.A.P. test to determine if the source is dependable.
Is it up-to-date?
Can you trust it?
Does the author cite sources?
What is the URL suffix?
Who is the author?
Does he/she have the authority to be writing/speaking about this topic?
Why are they publishing this?
-to sell you something?
-to convince you of something? etc.
More about the CRAP test is available from the Evaluating Information Guide.