guitarfreak...
for me personally, I think the secret to a good mix is in the tracking (recording) process. It really takes a long time to fully grasp why this is such a huge deal, but having steped in on a number of commercial mixing sessions, you start seeing the rediculous level of care that is taken into just recording a song.
There's a bit of an official saying that goes, "as a mix engineer, you're only as good as the recordings you get". That to me is gospel.
How that translates to you:
-Take the time to listen to your favorite mixes and make notes. How are the levels relative to each other? how was panning used? what makes this mix come alive?
Good contemporary engineers to look into are people like Andy Wallace, Chris and Tom Lord Alge, Ron Saint Germain, David Botrill, Terry Date...or more importantly, people who mixed the albums you like.
-develop and organize a plan that you can take with you anywhere. Mics will change, rooms will change, preamps and other gear will change, people will change, even your ears will change, but your ability to setup a recording session to get you in a ball park range of where you want to be shouldn't.
-Listening is a mental thing, not a physical thing. "Golden ears" have nothing to do with mixing great tracks. As long as you have relatively healthy ears, it's your ability to pick out and understand tones, timbres, and general go to frequencies that gets you where you want to go, and quick.
-Mixing well really doesn't come over night. Alot of times, even 4-5 years isn't enough time. You'll see that many of the better engineers have been around since the 60s, 70s, 80s or 90s. Not that I'm stereotyping, but some of these older guys really do keep on top for a specific reason: they stick to the fundamentals better than your up and coming engineers.
In other words, take the time to understand the basics of a good recording. Don't worry about slapping delays and reverbs all over the place just yet because you're going to frustrate yourself.
Learn how to live with just EQ, ambient micing and dynamic FX first.
-LEARN TO REFERENCE. Reference your mixes to other commercial mixes appropiate to the times. This will help you stay consistent.
-I think the last thing for now is you have to remember, mixing is subjective. This is an art, not a law. So don't beat yourself up if your mix dosn't sound like someone elses...who knows, maybe you've invented the next best technique that'll usher in a new generation of mixes.
just a thought.