- You need less gain/distortion on guitars than you think.
- You need less low end on guitars than you think.
- Avoid extreme use of EQ.
- Leave some of those imperfections - it makes the performance more interesting and human.
- High pass reverb so it doesn't muddy up the song.
- Make sure the instruments are properly intonated.
- Tune often.
some good ones worth repeating:
- Take a break often when mixing.
- Get the sound right at the source.
- Tweak the tracks for YOUR mix, not trying to match someone else's.