Great answers, save for the first.
I wouldn't dream of reinterpreting the great answers so far but would like to second the thought that objectivity is oh, so subjective. As in other fields of art, one can only judge based on experience, tastes and biases.
What I used to do when younger, when possible, was to glean as much info and tastes of a reviewer and compare it to what I heard, in a general way (much the same way as movie reviewers who I came to trust). Granted, it was much, much harder to audition the same components but aural clues figured large in listening appreciation as I learned the path to this hobby.
In the end it was every man for himself as I learned that what I liked, others didn't. What I disliked, others did. Consensus was akin to herding cats.
All the best,
Nonoise
