What are your criteria for deciding who knows what they're talking about? Every time I've looked into something controversial, I've found this to be one of the more difficult questions to answer.
The source should have some indication of standing - either an indication of training and experience in the direct (direct, not indirect - "I'm a structural engineer with 15 years of experience investigating skyscraper failures", not "I'm a mechanical engineer who's watched a lot of 911 Truth videos") subject under question, and/or an indication that they are conveying the consensus from those who do.
I look for sources which are neutral rather than ones who have a particular agenda. I look for information which was written for a different purpose than the one under consideration.
I look at the academic standing of the source - not in the sense of authority, but in the sense of the extent to which the idea will have been vetted to make it there.
I look at how topics on which I have expertise are handled. For example, if your method of looking into controversial subjects doesn't lead you to recognize that HIV denialism is nonsense, you're methods (and therefore your opinion) are useless.