Good work, if you can get it
Mixing is like art painting or engineering design (or both), depending upon whether you're right-brained or left-brained (or both.)You need to have an idea, a plan, before you adjust the first knob or push the first fader. In the case of mixing a song, you need to develop a mental image of what the final mix is going to sound like, where the instruments are going to be placed, how they are going to sound when they get there, where the hooks are and how to best use them, which riffs and fills should stand out and which should fall back, etc. This sonic design is crucial to a good mix, I believe.
Sometimes one has the sonic design figured out from the get go, which is an advantage especially if they are doing their own tracking. If one is mixing someone else's stuff, or if one made the mistake of not tracking with a particular sonic design already in mind, then they should sit down and listen to the tracks individually and in different groupings as needed and as mant times as needed before doing any actual mixing. Get to know both the overall feel as well as the detailed structure of the song with the view of building the mix design. Let the song itself dictate how you build the mix:
-Determine what and where the major hooks of the song are located and start building the mix around those.
-Determine what kind of emotion does it has in it's sound or in it's lyrics and how much of that emotion do you want reflected in the way it's mixed. A moody ballad and a rockin' anthem get different emphasies in the mix.
-Determine roughly where and when to automate the levels on the different instruments in order to showcase the best or most dramatically important music phrases for each track. When is the guitar more important than the piano and vice versa, and when do they both take a back seat to the vocals, etc.
Once the song has dictated and defined the above to you, then you can build your design of the 4-D soundstage to get the mix to fit right, sound right and move right. (see the DIY clinic thread for a detailed discussion between me and Tom @ Mastering House of the three or four dimensions of mixing; pan, spectrum, depth and drama.)
Put all that together and you have a dynamic mix with all parts sitting together nice and pretty with plenty of hooks and proper emotion. Not a bad list of things to get out of a mix
G.