- Powerful and solid lows
- Proper use of the very powerful mid range areas
- Clear and clean highs
- Proper but not overburdening effects
- Dimension - some sense of depth
- Motion - movement of the instruments using pans to heighten the music
- At least one true stereo track that sticks out "up front" in the mix. Usually the Instrument providing the hook melody like vocals
- Some acoustic information - not just delays and reverb   

The whole mixing process begins simply enough with a good pair of studio monitor speakers.While mixing on headphones gives you a great sonic experience, it won't translate correctly to speakers. Since headphones almost always have better bass and treble response than speakers, your final mix will sound dull and lifeless when you hear it "normally. Mixing is where all the hard decisions get made. It can make the difference between a amateur recording and an professional one, even starting with the same source material. This is why mixing is so critical. Also chose a mixer that has proven experience mixing within your musical genera. I've heard good songs not mixed well, and I've heard really bad music crafted into musical masterpieces.

The bottom line is that when it comes to mixing, the mixers who are the most creative are usually the most effective, regardless of the piece of music they're working with.