I respectfully disagree with you about that. Take yourself out of the equation and the song will write itself. Let the spirit be your guide.
There's some truth in that, but I was referring to playing a song, not writing one.
One does not sit down to play "Greensleeves" without pretty much knowing what notes they are going to play. Similarly, one should not sit down to mix their band's version of "Greensleeves" without pretty much knowing which notes by whom they are going to put where - or at least what their original plan for that is.
Just like a musician can improvise while playing, so can an engineer. But they should have some basic original plan on which they can improvise, otherwise it's just wasting time. If you have no idea of what you want to do, there's nothing to do. You don't just sit down in front of your DAW and say, "OK, now why am I here?"
And the best answer to that "why", IMHO, is to start with the arrangement and mentally set up a basic mix that "supports" it; by that I mean a basic mix plan in your head where one part of the arrangement doesn't sonically get in the way of another, especially in the signature elements of the song. As figuring that, figure whether you want a quasi-realistic type of soundstge, like Capt. Ego says when he says he wants it to sound like the listener is in the audience viewing the band on a stage, or whether you want to paint a totally abstract and artificial sound space, a la an Alan Parsons. Both are valid general options.
Use those guidelines, combined with however your muse tickles your ribs that day, as the basic "plan" with which you can start you mix plan, and just roll from there. And don't wait until after you record and are ready to start the mix to start this process. This is something you should be making at least mental notes about before you even start recording, as you're arranging the song and practicing it.
IMHO, YMMV, NBC, TMC, HSN, ETC.
G.