I just turned around my playtest/peer review comments yesterday, and already Nikki Vrtis turned around an updated copy.
- checking, again, for any issues or errors. If they exist I doubt I'll see them, it's hard to see your own writing with fresh eyes when you've seen it day after day for weeks.
- quotes! Time to find pull quotes from the text, and external quotes that match the material. I have some gems, I think, and I'm perusing some Vance, Zelazny, Gygax, Cook (Glen and Hughes, not related), Leiber, Pehov, Moorcock, and others for possible additional quotes. I'll see if I can't work in some cool song lyrics, too, but the material makes that a bit harder.
- dealing with "Special Thanks." I run a big campaign - I don't want to miss anyone who played a formative role!