Before I start mixing, I usually have < 25 tracks. I mute them, then turn on one by one starting with drums and bass. At that point, instrumental should sound solid already. Then I unmute all melodic instruments. If there is one Im not sure to keep it - I delete that (this is the hardest point - to delete something you been working on for some time)
Earlier, i had more tracks. I did stupid things like layering drums. Now if I dont like how it particular sound- I dont stack it all up, but just find best one. Also when arranging, there should be no 2 instruments playing on same octave. It makes mixing easier and overall sound much better.