When mixing, a lot of people say “man, I need to use this compressor, or use this eq, this will make my mix perfect” without thinking about some key factors before hand. See, a lot of people think they can just record at home, or in a basement studio and just take it to a professional engineer and he can make it sound like they recorded in a top of the line studio. While a good engineer can make it sound good, it is never going to sound like a industry quality mix, and that is because the mix quality depends heavily on the recording quality.
I have never been able to make a amateur, home studio recording sound like something that was recorded at our facility, or another professional recording facility, and that is not because of our lack of knowledge or experience, that is simply because there is only so much you can do. Mixing is not meant to be a process of fixing mistakes or recording errors, it is meant to be a process of getting everything to sound great together, and add some creative touch. A $100 mic tucked in a corner with some auralex foam from Guitar Center will never sound like a recording in an acoustical treated room with good quality mic, good preamp and good compression (if compressing while tracking). Sure, there are home studios out there that have spent the time and money on treating their room, and buying some good gear, but we are speaking more on the low level artists who are just starting out. So if you really want to get a great mix, think about the recording as well, don’t sell yourself short by thinking you can just record anywhere with anything, and rely on someone to fix the mistakes that were made while recording. Plan ahead, and get it done right!!