Well, there are basically two ways about it.

Way one is deciding that you will trust somebody, so you listen to what he/she/it says and you're done. Advantages: easy. Disadvantages: obvious.

Way two is reading through a lot of conflicting materials (mostly papers), filtering out people who are stupid, who have an axe to grind, who have been regurgitating cached thoughts for the last couple of decades, etc. and then trying to construct a mostly coherent picture out of what remains. Advantages: you will understand the field. Disadvantage: hard, expensive in time and effort, involves wading through rivers of bullshit.

I am not the trusting kind, so I read the papers :-)