I really liked how Never Unprepared spelled out the steps to session prep in a deliberate fashion, and intentionally separated some steps that you might be tempted to mash together, so that you are more likely to deliberately think about the individual steps and put the proper amount of work and thought into those steps.
Alas, I have to admit, I don't follow all of those steps all of the time. There are times when I really get on a roll, and I just can't stop and force myself to hit all of the steps along the way, or I'll lose what it is I want to capture in my outline for the next session.
So, does that mean the session prep steps are wasted on me, or don't provide enduring advice? Not at all. I've found that slowing down and deliberately going through the steps whenever I've been stumped for actually starting my next adventure has been a great way to center myself and get some ideas in order. Turns out, when you deliberately go through these steps, you often find out you aren't out of ideas so much as you have to put in some effort to get them to connect.
So while I don't follow all of the prep steps every session, having them available has really helped me on those off weeks when I just can't get the floodgates open. Even when I am on a roll, while I might not stop and do the steps separately, I have often caught myself thinking that I just moved from one phase of prep to another, and sometimes back again, when I get going.
There is one specific part of the prep process that has really stuck with me, and that is having a specific Review phase. I am much more likely to force myself to stop and think about how I've presented an adventure, and look for what I might have missed, than I was in the past. I've caught myself a few times thinking "I never put in here where they were suppose to find that key, but I'm assuming they have it for this section," which was the kind of thing that threw me into heavy improv mode in the past.
While there is nothing wrong with heavy improv mode, I'd much rather fall into that mode because the players do something completely off the wall than because I forgot something really simple and mundane that should have been part of the plot from the beginning.
Another thing that the book helped me to realize, that has stuck with me, is that using the right tools for how you work is important. For a long time I was using only electronic tools to prepare my games. In many situations, that was because I was running much more rules heavy systems like Pathfinder or Mutants and Masterminds, and since I was already on the computer, I keep working on the computer.
I've realized since reading Never Unprepared that, while some electronic prep is fine (printing out stat blocks from PDFs that I own, for example), a lot of my creativity comes to me when I'm writing in a notebook using a pen. Working on the computer almost makes me feel like I have to write for some third party that might review the adventure, but writing in my notebook, I feel like I have permission to just use whatever short hand I'm going to understand to get the ideas across to myself.
So in the end, while I may not be a perfect disciple of the techniques, I will definitely say that I picked up some useful traits from Never Unprepared that have stuck with me, and that I am glad to have developed.