Whenever an editor or agent is lured into listing the things which put them off a manuscript, it seems that well up the list is a novel which starts with someone waking up. And top of the list is the subset of these which start with the protagonist waking up with a hangover or a head wound. "But - but - but -" thousands of aspiring writers cry, and they have a point. What about Kafka's The Metamorphosis, just for a start, when Gregor Samsa wakes up and discovers he's become a beetle? Indeed, the unrevised version of my new novel began with someone being woken up, and if that narrator hadn't been axed in revisions it still would: the opening wasn't the problem.
As so often, when agents and editors start talking, they're talking about what they see - the many waking-up openings that don't work - and they blame the waking up for it, not the not-working. That doesn't mean it's not worth knowing these things about agently reactions; if you're doing something agents know from experience is usually done badly (prologues are another example) then your mss is starting off on the back foot, and you'd better make extra-sure that it works in every other way. But, fundamentally, when a waking-up opening fails it isn't because it's a scene involving a duvet and pillows (or a stained horseblanket and heap of straw), or that the next paragraph starts with drawing back curtains or hacking down the stable door. It's because of what follows the first sentence: a description of the world into which the protagonist has woken up. Description. It may be wonderful (or hangoverly disgusting) sensory detail; poetical or horrifying scene-setting; compelling character-description; intriguing memory (hazily wonderful or hazily horrible) or backstory; witty or heartbreaking reflection, but it's going to be a while before things begin to change, and change is the motor of fiction. It's not that the first sentence needs to be about the SAS abseiling through the window, though there are worse ways to start a novel. Gregor Samsa doesn't (as I remember, since my copy seems to have taking a walk from its proper place, between The Leopard and The Unbearable Lightness of Being) do anything except lie there on his back and look at his claws.
And there's the key. Lying on your back is suddenly quite a different thing if you've turned into a beetle: unstable literally, and unstable metaphorically. Absolutely built in to that very first sentence is the knowledge that something has to happen: first, he's got to get off his back. And then what? Whereas if your plans for the story don't include coleopterology (yes, I did have to look that one up), then you'd better make sure that the instability is built in other ways; my narrator didn't wake up, he was woken up, by someone with a very serious problem banging on his door, and my agent approved of it as an opening. If the only instability in your protagonist's situation is the alcohol in his stomach, even those of your readers who aren't vomit-phobic are likely to think at some level, 'So what?'
Of course, as I was discussing in Why Should I Bother?, if it's a writer you know and love, or the voice is incredibly seductive, or the texture of the writing irresistible, the reader may go with the flow for a while. And the experienced reader, or the reader who isn't on her seventieth slushpile manuscript that Friday afternoon, may be able and willing to pick up delicate clues to an instability that isn't, yet, being spelt out. But, what, on that very first page, tells the reader that something has to happen? We wonder how Gregor got like that, but much, much more urgent is the question of what, physically, now, he's going to do about it? Not what has happened, but what will happen?
But, if your novel or story opens like this, please don't beat yourself up. It's a very natural outcome of how you, the writer, have been thinking about the story. You've had to think your characters up to their starting point: their physical, mental, emotional and practical situation as the story kicks off. You've been dreaming them, and these not-working waking-up scenes are part of your dream: good first-draft stuff. Now it's you who need to wake up, and re-write.