The way a GM sets up their personal fortress of solitude at the gaming table is very indicative of their style. Some GMs run their games behind a stack of books and official published material, while some GMs run their games with just a pair of dice, a pencil, and a notepad. Some of us turn everything digital and call their laptop savior, while some of us make elaborate binders and organizers full of information.
If the GM plays it fast and loose without dipping into the published material or setting, then the players are going to feel less limited in what they can do, but will also have to put more work into figuring out how the GM might interpret a certain rule. If the GM runs by the book (and the setting book, and the expanded psionics rules, and the optional 3rd party magic system, etc.) then the players know where to find source material and can be fairly assured the way the book lays it out is the way it will be in game.
If the GM likes to take the rules and reorganize them in their own way (via laptop, or binder, or personal kobold assistant) then there is a fair chance that the elements of the game are going to be well thought out, but with a bit of personal interpretation of the source material and house rules applied.
So what is your personal GMing toolbox like? What do you think it says about your style as a GM? For that matter what do the tools you use as a player say about your style?