Captain OCD here! I preview each workout when I first get it, typing-in notes in Word about the exercises and weights that Cathe uses. I then print that out and use it to make notes as I do the workout, including which weights I used. I update the Word doc with those notes, print out a fresh copy, and keep that in a binder for when I do it next. I have an exercise breakdown for all but a handful of Cathe's workouts, including the live ones! I've been doing this for about 16 years, I think. As another poster noted, it's nice to be able to see what weights you've used previously, and how you've progressed.
I don't do formal rotations (caveat: I did do STS once). One of the reasons I really clicked with Cathe is that she offers so many different workouts. If I had to be rigorous and plan everything in advance, I wouldn't be able to make myself work out.
I also keep an Access database where I track which workout I did on which day, along with data from my heart rate monitor. It's cool to be able to compare the data to see which workouts have the highest average calorie burn, for instance (for me, that's HIIT 40/20).