How do you train your ears?

Listen, listen, and when you think you are an expert listener,
listen some more.

WHAT ? oh sorry that was when I was married. Now I just simply RELAX! Cheers

Listening and hearing are two different activities. I like listening to music. I enjoy it more when the performers are into it. I get more out recorded performances when the band is 'on' than live performances when the band is having an 'off' night. Otherwise, the best training for listening is listening. I could not imagine going to a live concert in order to train myself to listen to my stereo better. I go for the music, the fact that it is an 'event' and the performers want to please the crowd, the fact that I might be going with friends who also look forward to it. I go for the chance to see my wife all dressed up, for the dinner before, and the maybe the drinks afterward. I go to listen to new music, a new performer, a new interpretation, or to again listen to something I heard years ago.

I have found it very helpful to listen to what other knowledgeable people say. People who have been in the hobby for a number of years. Have them go out to listen to systems with you either at dealers or other friends. You don't have to agree with them but often they bring up important issues that may not have occurred to you.

An analogy to this would learning about wine. You go wine tasting and have the wine server give you his take on the flavors in the wine.

Just a comment about commcat's post. I have no doubt that the tapes you and the engineer heard at your home sounded like the live performance. However, I once did an amateur stereo recording of a community-produced musical in an auditorium. I was a kid, it was 1977 - and used my Superscope Dolby cassette deck and a pair of $15 RatShack mics set up on a table about 10 feet back from the stage. Everyone who heard my unedited cassette recording was astounded at how much like the original it sounded, in spite of the obvious lack of fidelity of the recording chain and playback gear (my old stereo was OK, but mid-fi - Advent New Large, Kenwood receiver and the afformentioned Superscope deck).

Why? My theory is that all who heard the recording were present at the performance (or in it), and had some memory of the acoustic environment. Since my amateur setup captured the echos of that auditorium, the recording sounded like the live event. This effect was especially true when using headphones (I had Sennheisser 424X cans) fed from the cassette deck's headphone jack. Just my $0.02.