I'm a VERY random editor. I tend to write and edit as the mood strikes me (writing's a part-time hobby right now, so I'm not under any deadlines at the moment). If I get a scene concretely in my head (as in I can almost 'see' it like a movie), I have to write it, just to get it out there. But then there's other times where I write a scene, then start 'seeing' it in my head and will go back and re-write it.
Basically, I edit scene by scene until each scene has been worked over three or four times (at least). I usually edit on screen, and change the color of the words after I've edited a certain scene. When I'm halfway through editing, my manuscript looks like a rainbow!
Then I start at the beginning and work through it systematically (again, changing the colors as I go along). Eventually, all the font is a nice blue color (since I start with blue, and after each scene has had its final edit, change it to match the scene ahead of it), and I can 'select all' 'change color' 'black' and print it out.
I find I don't make a lot of typos or punctuation mistakes, and most of these get caught in one of my scene edits.