I was originally going to write about adventure planning in the same spirit as what +Ryan M. Danks posted about Adventure Fractals. Instead it's taken a turn toward campaigns and not just adventures. I've actually written previously about this subject on Dreams of Flesh and Spirit, and some of those concepts are going to be making a reappearance.
I'm preparing to run Children of Lilith, the first of the Tribe 8 metaplot books, using my Fate of Vimary adaptation. I've run some Fate before, but it's never been quite as grandiose and setting-spanning/altering as the Tribe 8 metaplot. I have run CoL before - twice, as a matter of fact. It is a reasonably well-done campaign book, considering it's anchored in the mid to late 90s school of plotted campaign design. That means it's laid out in a linear fashion, with a lot of movement from one pre-planned event to another, and is easily completely derailed (in one Tribe 8 game, a PC's reaction to an event wound up removing three major NPCs and made it impossible for one of the plot events to take place). It also can come across as The Named NPC Show Co-Starring The PCs. There's a lot of talk about how important the PCs are and how they should be involved, but as written the story can kind of run on autopilot. It should be pretty easy to see that marrying the existing metaplot structure to Fate Core (or any narrative-focused game, for that matter) is going to need some mild tweaking. Well...more like a complete gutting.
My solution to pacing and handling potentially complex metaplot events in a game like Fate Core is the milestone fractal. It's inspired by the adventure fractal, and similar to Legend of Anglerre's plot stress, but differs in a number of ways. It's a way of pacing the campaign as a whole.
The first step in creating a milestone fractal would be to define one or more milestones. In nearly every way, this is a normal campaign milestone. This means there should be an issue or defining aspect involved (but not always). Basically something that the players want or need to accomplish. In cases where there is an aspect, that aspect will change or be added once the milestone is achieved. Whether the players know what the new aspect will be or not depends on the goals and the campaign.
The milestone would have a stress track, very much like an adventure fractal's - three stress, with the number of PCs used as a skill rank to determine if more boxes should be added, and three consequences (mild, moderate and severe). Instead of the PCs dealing stress to the track by making a skill roll, the stress comes from predetermined events. This can be the completion of specific adventures, campaign arcs, achieving goals, whatever works for the campaign. To maintain fluidity these events should not have to happen in any particular order unless absolutely necessary - in fact, if the PCs do something that's not on the list which would affect the milestone, it should deal stress as well. If you need to pace when the campaign milestones are achieved, you can use the Consequences to absorb the stress.
Since we're treating campaign milestones as characters, it's entirely possible to give the milestone itself a skill or two or even stunts. I don't think there's really a standard skill list for milestones though, because it's going to depend a lot on the campaign and the nature of the milestone. However, the wonderful Spark rpg from Genesis of Legend Publishing has the concept of the setting itself having attributes. It's list of four attributes (Body, Heart, Mind and Spark) are a good starting point for determining what skills a milestone might have.
Also worth noting is that the PCs don't necessarily have to work on one milestone at a time. If you already have a few milestones defined - or if one becomes obvious that it needs to be defined - then events that transpire can logically apply to two at once, or something the PCs do can mark off stress on a milestone track they are not currently on. Again, you can control pacing through using Consequences. This is especially useful when dealing with timing - if one milestone involves replacing corrupt councilmembers and the other one involves taking down the local crime syndicate, moving too quickly on the syndicate while the councilmembers are still in place may have other repercussions.
The cool thing about this setup is Ryan's adventure fractals should be able to nest comfortably inside a campaign milestone. Several adventures might comprise an arc which culminates in a minor campaign milestone. A number of arcs are a campaign, which is a major campaign milestone. Tribe 8's metaplot books are actually already set up this way. It's just a matter of breaking out the specific, step-by-step events within each of the individual chapters and determining where the milestones are. I smell a mindmap coming on.