Trained ears.

But yes, hopefully the listening is immersive and deeply and emotionally joyful....

there is a music section of the board here, what’s on your turntable tonight is my favorite...thread but there are others for CD, streaming, even live music. not so much gear and technical talk....late nite crazy marathon listening is the norm.....

What is complex is to tune the system like an instrument. You have a few components working together that must become the one. This does require experience and some knowledge in addition to hearing. And don't forget the room - it is probably the most important single component, provided the rest are good enough. One wrong set of cones under one component and the system is out of tune to various degree, wrong platform under turntable and it's no good, wrong or not quite right power cord on your Studer deck and something is lacking.

First make clear you have a balanced system. All music should sound eaually fine (or bad). The system should not favourize any specifical type of music. Make sure every recording you play sounds different. That you can hear differentiate between good and bad recordings. That you can separate individual instruments and singers and follow their lines. And that the transparence and dynamics makes you get a "live" feeling.
Then we have the question if it sounds correct. Play the piano someone says. I probably have a piano on thousands of recordings. No one sounds the same. What is correct? If it sounds natural it's ok. Only if you were there and did the recording yourself you would have a chance to know. 
Read between the lines. Lots of exaggerations when audiophiles discuss "huge" differences between dacs, amps, IC's whatever. In reality very small differences, maybe probable to hear if you really want to and are searching for them. Fun, but not sure if it really matters.  

Agree to all , N80 your number 4 is very very very true Listen listen listen listen listen, spend time listening, If you have two systems helps too....

When i began my journey on a another, enjoyable, frustrating, subjective hobby - wine -- i asked a great sommelier the same question. His answer: pop a lot of corks, and think abotu what you are tasting".
I learned not onyl to taste wine and what was good, btu more importantly what i liked and what it might do well with.
G