I'll add the one tip that I believe has helped my mixes more than any other:

High pass filter nearly every track excepting bass lines and kick drums. Where you high pass depends on the source and what sounds right.

This works particularly well on vocals and any other mic'ed track you might have at home. With my vocals, I usually filter somewhere between 120 and 200 Hz, depending on the song.

This is a fairly unsophisticated technique, but incredibly valuable. When tracking, if you have a low-cut switch on your mic, it's almost always advantageous to engage it; again, except for kick drum or tracks that intentionally should have the lowest frequency content in it.

Try it, you'll like it.

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