Just thought I'd throw this out there in case anyone else struggles with the same things I do...
I've been following, reading, researching, and fan-stalking Fate since the kickstarter was first announced, and I have run about a dozen games (not many, I know, but finding game groups is hard). In spite of all of that, there are still a couple pieces of Fate mechanics that tripped me up, probably because I was born and raised on d100 and d20 systems.
My largest struggle as a GM is the concept of "Success at a Cost" (Or "Failing Forward"). I get it, conceptually. A stark, "No, you fail" that has no consequences beyond being unable to advance bogs down the story and game, but once I'm actually sitting behind the screen and one of the PCs botches a skill roll, my default is still to just say "No".
Recently, in my quest to hack a GME together for Fate (more on that later) I read through the FU system, and its task resolution system helped me understand Success with a Cost. In FU, there aren't just "Yes" and "No" answers (like in most d20/d100 systems), there are yes/no, and/but answers. AKA instead of just saying, "No, you didn't talk your way past the bouncer," say "No, you didn't talk your way past the bouncer, BUT he did let slip that the Senator will be leaving in 30 minutes or so..."
In play, I've made a rule for myself that I can NEVER say "No". I can only say "No, but" or "No, and". In some situations (most notably combat) these things are built in automatically, "No, you didn't parry his blade AND it slips under your ribs."
But in more straightforward "Skill Checks", this requires me to think creatively.
Terry is pouring over dusty tomes in a university basement in a race to uncover the secret to disrupt a powerful ritual her nemesis will soon use to summon and bind a powerful demon...
Her player rolls a total of +1, failing by 3: "No, you find no clues to stop this ritual, AND as you slam the tome closed in frustration, the lights in the basement go out and you hear the sound of clawed feet scraping across the bare concrete floors behind the bookshelves. Somebody doesn't appreciate you poking around here..."
Her player rolls a total of +3, failing by 1: "No, this book doesn't contain the knowledge you seek, BUT as you are about to slam the book closed, you notice a scribbled note in the margins of the page you were looking at. You'd recognize that handwriting anywhere. It seems it's time to pay your old anthropology professor a visit..."
Both of these options are MUCH better than just saying, "Nope, you didn't find anything. What do you now?"
As a bonus, the "Yes, but" option works well for ties/Succeeding at a minor cost- "Yes, you find the information you seek, however, it requires a pint of blood given freely by an pure soul under the light of the full moon. The full moon is tomorrow night. Where are you going to find this pure soul?
Hopefully this little ramble will help someone out there understand Fate a little better!