Clueless......Absolutely Clueless

I have made it to level 86 on this hunter, soon to be 87 and I have NO IDEA WHAT I AM DOING.
I also have an 86 Warrior and have NO IDEA WHAT I AM DOING. Like I'm pretty sure there is a science or art to this game, hence why raiding is so "Hardcore" and time esteemed....But I have no idea what I am doing.

I literally just spend a few hours a day in a LFG queue and go through dungeons just using whatever ability I damn well feel like, and have yet to have issue.

Any guidance on how to properly play this class would be appreciated. And I don't mean ElitistJerks, cause that site is about as legible as reading a law document.