Well, in my opinion people are overthinking the whole mixing thing. When I do my tracks, there is no such a thing like a mixing stage. I mix the track while I'm producing it. Because I might bend different sounds together and use effects and such, to create a complete new sound from these other sounds. And I do that with EQ, compression, reverb etc. which are all part of the mixing procedure. But I know with what I start in my track, and with what I finish it, because every new track I will add will be mixed to what's already there. So this is something to think about - I usually start with the kicks, then the bass and the melody at the same time, and then go on from there. I add the less important things to the end, like sweeps or crashes. So basically, my bass and my (melody) synth will be mixed to my kick, which is the key element here. In the end, my sweeps and my crashes will be mixed to almost the whole track. See my point?
Of course, during the production stage I will always adjust all levels correctly. And at the end again of course, to fine-tune everything. But, like I said before, I would bend sounds to obtain another sound. For example, my bass are actually 4 basses. The way they're mixed will decide what TYPE of bass and what SOUND it will have. So I have to do this before even going on, because it will stay like that and I want to mix the rest of the track to how I WANT this bass to be. I don't know how to explain deeper. If this bass is not mixed correctly (or the way I want it), it could give a complete different sound. This is my point.
Every time I add a new track, a new sound or whatever, I instantly "mix" it. I add an EQ and cut everything I don't need away. I would add a reverb, cut some lows from the reverb again, see how it fits with the rest. Then adding a compressor eventually, side-chaining it maybe, seeing how it works with the track... etc etc. And then I move on to the next sound.
