I like what David said. Air.

Essentially, giving everything it's own space in the mix.
This is accomplished by several things.
Use the minimum number of tracks possible. Just because you have 20 tracks does not mean you have to use them all.
Panning. Self explanatory.
Judiciously using EQ. For example, cutting the lows from the guitar will let it sit cleanly in the mix without mud.
Being aware of different instruments that share the same sonic space.
Use hard envelopes for volume. Don't let things ride at -20dB. If they are not the rhythm section, a fill or solo, they probably don't need to be there. Take them out totally. Don't create mud and chaos.

That's a good starting point.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.