There is no “real” rule to mix a song. It’s up to you to decide what you want to get from your mix and everyone who’s into mixing like to have a series of personal rules that they follow and it’s completely right. There’s nothing wrong if you follow “no real rule”. At the end of the they you have to mix and your final result it’s the most important thing, doesn’t matter how you reach it, even if you need 6 days to complete it or just 6 hours: the final best mixdown is the target. Anyway, if you try to follow some guidelines that really help you there’s nothing wrong and I have to say that I found some guidelines really helpfull in smoothing my mixing activities. It’s all about a series of actions that bring you to the very preliminar mix. Before you mix.
I see it a lot of times, even during my sessions, I always pay not too much attention to the consistency of the tracks, because I’m eager to start mixing and I want to start insert plugins everywhere and moving knobs. But we have to keep in mind that editing is to be concluded before the mixing session. When it’s time to mix the starting point must be a series of consistent tracks, with no timing issue and with the vocals and choirs in tune and so on. If this is not your starting material you have to stop and fix it. If you don’t do it you’ll always be distracted during the mixing session by this issues. When you stop thinking about EQ and compression on your tracks just to edit some timing problem you’re losing the right focus. When you mix you just have to mix. You could decide to mix it even if it’s not so consistent, but you’ll never get the best result from drums with timing issues, or from a vocal part out of tune. So it’s always better to end the editing phase before the mixing part of your work, once and for all, to keep focused on the right things during the mix.
After that, the first thing that I do is just listen to the tracks as they are, without touching anything on my DAW, just noting the song structure and my ideas on the future mix on a piece of paper with a pen, but you can do it even on your text editor on your pc, it’s just listening and noting. After that, it’s time to play again the song, but now, start adjusting the volume fader of each track to put all in its right place. Pretend that all that you have on your DAW is the volume fader. After this first “volume mixing” it’s time to pan the tracks. Usually I like to think about panning to “fixed” positions: Left, Center, Right. Nothing more, for the most part. For example this is how I pan the drums (but this is not a rule, sometimes it just works better with different settings, experiment as you think it’s best):
Kick, Snare, Tom 2: Center
HiHat: 80% Left
Ride (if you have a separate mic for the ride): 80% Right
2 Overheads mics: 100% Left + 100% Right
Tom 1: 100% Left
Floor Tom: 100% Right
This is what you can do even with other instruments and vocals, think about the song you’re going to mix and try to imagine each instrument placed in a room, pan the instrument according to the position you’d like to hear the sound coming from. It’s a quite creative moment, you’ll love it.
When you think you’re ok with it, listen again. You’ll be surpised how much better everything sounds now: volumes are more controlled and everything it’s in the right place. Now it’s time to mix! You’ll fine how muxh better you can focus on just the best choices for your mix, on the right settings for EQ and compression on the tracks, untill you can start adding FX on your sends and adding automations and so on. Now you’re free to mix with no other issues bothering you. Maybe it’s a time consuming procedure, but trust me, it’s definitely worth!