A lot of folks recently had a big hate-on for Blake Snyder's Beat Sheet, and some of the anger is fully justified. Snyder was a screenwriter, and the BS2, as it's called, is a pure, formulaic layout of a script's emotional highs and lows. It's such a reliable formula that every blockbuster recently has been written to it. Hit the Slate link for the details, and one you memorize it you start to see just how every movie is written to it, "Mad-Libs" style.
I don't write for the screen. So, as a words-on-paper pantser (someone who just sits down an writes, to hell with an outline or formula) , mostly, I don't advocate or think much of Snyder's formula. There is, however, one thing that he illuminated for me that I've been thinking much more about recently as I write.
Deliver on your premise.
The theme, if you even bother to think of one, is a pithy, one-sentence notion of the philosophical push behind the story: "Love conquers all," "Simple is better than complicated," "Beauty fades, but brains are for life." The plot is what happens, the pace of scenes, the rise and fall of emotional beats you want the audience to feel as they read your story.
Premise is something else entirely. Premise is delivering on the kind of story promised by your opening paragraphs. Star Wars promises spaceships shooting at each other; Star Trek promises exploring "new life, and new civilizations, boldly going where no one has gone before." (This explains why I loathe the J.J. Abrams Star Trek franchise.) Harry Potter promises wizardly battles, magical hijinks and teenage derring-do. Any Banks' Culture novel promises enormous, creative vistas of shock and awe within which surprisingly petty people continue to do their petty things. Weber's and Bujold's novels always deliver on the premise: long before the final reveal, there's a long stretch where Honor or Miles are doing what they're really all about: making other people become better people by example.
The premise is the fun part of the story, it's the part where the audience gets what it came for, not in the small drips and drabs and hints and promises of the first few chapters, but in a long stretch where we get to see the character in his or her new element, confronting the challenge and excelling. Not good enough, quite, to vanquish the crisis, which must of course rise in power to meet and exceed the protagonist's efforts.
As I write erotica, the theme can be lots of different things-- the rising or fading of desire, love conquers all, fear of failure, etc. The plot can be all over the place. The premise is that "the characters have sex," and my responsibility is to get them there as fully realized and justified characters, and to make the sex act a central and revelatory scene, and to show how the consequences of that scene lead to the ending.
Whatever your premise is, deliver on it. Moon, Sun, Dragons has a problem in that the middle part of the book must show Cheilleine and Sarah successfully leading the charge to kill the dragons; Sword of the Bankers (my "What if the Medici had had a few Jedi to work with?" novel) must somehow show Janae learning to appreciate her powers, and enjoy using them even as she unravels the way the power structures in Italy and Denmark conspire to maintain power. Somehow, I haven't quite reached the point where I could deliver on those.
But I can deliver on short stories of people boinking. It's what I'm good at. So I'll keep delivering on that, at any rate.