I don't have any set rules, but there are a few things I normally do. I usually color code the individual tracks first and get them sorted by instrument groups. Makes it much easier to get an overview and create sub-groups, especially if there are lots of tracks. At the same time I listen to the whole thing with every fader up, if possible, to decide the direction of the mix and pick out the most important elements. After that I would probably work on the key parts, usually vocals, drums (kick, snare and OH), bass, acoustic / electric rhythm guitar or piano to make them to work well together, using HPFs, maybe EQ, compression, reverb, and build the mix from there.