My question for y'all is: how do you keep track of the details, for yourself?
The exact system I use will depend on the specific needs of the campaign/adventure, but it ultimately boils down to identifying usable chunks of data and grouping it together.
For example, my current campaign is organized around two key documents:
(1) Adventure Track
(2) Campaign Status
The former lists every "adventure" I'm going to use as part of the campaign and also includes the revelation list that will move the PCs from one adventure to the next. (Some of these adventures are locations; others are organizations; others are events.)
In the case of my current campaign, the Adventure Track is broken down into five acts. One of these five acts involves two largely separate plots -- they occasionally intertwine, but they're generally interdependent enough that I'm keeping track of them in two separate lists with two separate revelation lists.
The Campaign Status document, on the other hand, is a current snapshot of the campaign. For my current campaign that includes a schedule of upcoming events (08/09/1089 - the third assassination attempt on Emily); a schedule of upcoming backdrop events (that will be reported in newspapers); and the current status of any "adventures" that the PCs are currently interacting with (they've killed X; cleared out areas 8-19 of dungeon Y; the cultists have reinforced the Tempestwarren; etc.).
Each "adventure" is contained in a separate Word document.
There a couple of other miscellaneous documents to catch odd bits of data: An Excel spreadsheet for tracking a particularly complex and inter-related series of handouts. A separate Word document containing the secret history of some amnesiac PCs. Et cetera.
Oh, and I keep a detailed campaign journal for every single session. They chew up a ton of time, but well worth the effort.
But what it really boils down is identifying usable chunks. And if, necessary, creating a heirarchy of usable chunks within usable chunks until you get to the point where you can manipulate comfortably at a macro level and zoom in for the appropriate level of detail at will.