When discussing the recording process with musicians, I always finds myself saying , "mixing is everything-one can take a good recording and destroy its sonic quality by doing a lousy mix. On the flip side of that, you can take a mediocre or poor recording and with the right person and gear, create an excellent mix".

This is true because of the huge difference between how people use studio gear and how different their "ears" are. Obviously, to get the best results for your project, you want to be recording with people who are very experienced and also have good "ears". Also, it's important that they have a similar "sonic/musical vision" as you.

Put five different people in front of the same mix at the same studio and the results will have an incredible range of quality and approach. Adding in the fact that there are many other elements besides people that determine how good your mix sounds, it's not surprising that I get so many calls from people who are not happy with their final mixes. Some of these other elements include: a control room that is not "tuned" properly (making it untruthful for listening) and the sonic quality of the gear being used.

Recently, an artist/client/friend of mine from New England recorded a song using a different Engineer/Producer for the first time in 13 years. When it was finished, I received a call expressing her concern about the final mix. The major complaint seemed to be a "muddy quality with no drive or punch". After listening to the cassette myself, I could tell that there were indeed some problems .
Not having access to the original multi-track tapes and the DAT mix master, it was hard to know whether it was just a poor mix job or whether the original recorded tracks were the problem. My client brought the tapes to Toronto, and on listening to them I discovered that approximately 75% of the problem was in fact, the mix. The remaining problem was a combination of a few poorly recorded tracks, and the inclusion of some tracks containing musical performances that cluttered up the song.
Using a similar type of studio as the original tracks were recorded and mixed in, and utilizing most of the original tracks, I did a new mix. According to my client and the other 3 musicians on the project, the comparison between the two mixes was like night and day. The new mix was clean, clear and had a definite, driving, punchy low end. What made such a big difference? As much as people tend to call me this, I am NOT a magician.
I simply EQed the other recorded tracks to make room for the bass and in general, edited out any unnecessary musical clutter.
These two aspects (besides a different sonic/musical vision), were the other Engineer's biggest problems. Naturally, making room for the low end isn't the only thing that makes a good clean mix, but it certainly is a good place to start. An example of how this is done can be seen in this next story.

I was helping a guest engineer with a mix at one of the studios that I work in and after many hours, he said that he couldn't seem to get a bass sound that he was happy with. He gave me permission to go in the control room and do whatever I thought necessary to help clean it up. The first thing I noticed when looking at the console was that every channel had a significant EQ boost in the mid-low or low end. As soon as I cut back on some of this EQ across the board, compressed the bass track a little more and brought up the kick drum, suddenly the low end had more punch.
As much as I understand the desire to have every track sound nice and fat, this EQ approach in terms of the overall picture, will create a muddy low end. The single best way to have a cleaner mix is to EQ most of the tracks, other than the bass, to be a little on the thin side. Also, when using EQ, get into the practice of cutting frequencies rather than boosting.
The subject of clutter is much more of a personal issue. Everyone has different tastes when it comes to how much instrumentation should go into a song. During the mix process, if your Producer and/or Engineer suggests a slight change in the concept of the arrangement in an effort to obtain cleaner results, try and be open to it. Don't assume that every recorded track has to survive the mix. You may find the wiser choice is to let go of some of the tracks that clutter the song and detract from the overall musical vision. Remember, sometimes "less is more!".