The best guys know the theory of what parts of the frequency spectrum to adjust for any given situation.....BUT they also use their ears......using ears and tech knowledge of the sound spectrum is a lethal combination.
I always remember a guy explaining about adding in parts of the spectrum that were outside human hearing. What difference it makes is actually audible cause the part you cannot hear can have an effect on the part you can making it sound a bit different.
Generally I leave that side of things to the experts.......despite a lot of the stuff being "geeky" they can make your tracks sound a whole lot better. I have not the time or patience to even start.

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055