Perhaps the most essential skill for a writer is this: the ability to spot and discard a bad idea before you've wasted time and invested emotion trying to write it.

It's not something I've ever formulated, preferring to judge story ideas by their shape or feel rather than by running them past a technical rule, technical rules being always subject to exceptions, but the other day I stumbled on a surprisingly useful way of defining it.

Christmas is a time of ghost stories and I'm a great admirer of M.R. James. My husband observed that his stories tend to take place in a rather cosy world, or at least cosy until the ghost homes in, and I was thinking about other cosy genres. I thought, 'You know what might be interesting? A ghost story set in a chick fic world.'

Then I thought, almost immediately, 'Nope. That idea doesn't work: bin it. Moving swiftly on...'

My husband asked why I'd rejected it so fast, and I said, groping of a phrase, 'I couldn't write it. There's nothing there. It's an idea about a story rather than an idea for a story.'

And that's it: that's the problem with a lot of unusable ideas.

An idea for a story is concrete. Generally you need at least one major character, a setting that will bring them into contact with other people and some opening event or situation that they'll be reacting to, but the important thing is that there's content to the idea, that it's specific. You can sit down and start writing it: it was a rule of mine when I was first teaching myself to write that the best way to try out an idea was to write a page of it, and if there wasn't enough to base a story on by the bottom of the page, drop it. You need to begin with quite a lot of material, or at least, several definite things that you can bang together to knock a story out of them.

An idea about a story is abstract. It's a description to yourself of what the story might look like once it was finished, a concept with no tangible examples to make it real. It sounds good, but that's because you're mentally describing a non-existent story: you can fancy it as good as you please, because there's nothing there to contradict you.

An idea for a story starts at the beginning and from the inside; an idea about a story pictures the story as an already-completed object and views it from the outside. If an idea for a story is the beginnings of a blueprint, an idea about a story is effectively the jacket blurb to a piece that nobody's written.

So to give an example: a ghost story set in a chick fic world is an idea about a story. There are no characters - 'chick fic' implies some very nebulous stereotypes and nothing more - no situation, no starting incident or destined end, no ghost, no stuff. All it really does is allude vaguely to works other people have already finished. At most, it's an idea about style, and you can't write style if you don't have something to write about. An idea for a story would be about, let's say, Susie who works in PR and has been waiting a long time for promotion, and when her sleazy boss sends her on an away conference, she runs into her ex at the hotel, and also finds a mysterious figure always sitting on the other side of the steam room every time she uses the hotel spa, never speaking, never quite discernable, but a little closer to her every time she goes in. That's an idea for a story: there's no ending yet, and things might change in the writing of it, but you've got some characters, something for them to do and a situation for them to inhabit. It might be a good story, it might be a bad one - running it past my own sensors, I suspect it wouldn't come out in a chick-fic style, which just goes to prove even more that the idea-about wasn't something I could use - but it is, at least, an idea for a story, not about one.

Ideas about stories can sound seductive, and I think one reason is that we live in a world of packaging. If a marketer can say 'It's Raymond Chandler meets P.G. Wodehouse' or 'It's about medieval France from a feminist perspective', they'll find the product easier to sell. We hear so much of this kind of talk, one can start thinking that this is what story ideas are. But the trouble is, these are descriptions of stories that are already written, made by people who didn't do the writing. They're not a very good guide to approaching a story you want to compose.

Ideas about stories can drive you to distraction. Their fatal flaw is this: because they're not confined by specifics, there's no limit to how good they can sound. In effect, they're fantasies about having written something, and in fantasies, everyone's a genius. Come up with an idea about a story, and it can seem like a brilliant wheeze. Usually you'll delay writing it, mostly because you don't actually know how to start (because you don't have anything to start with), and the longer you delay, the better the story can look because the further into fantasy it retreats. In the end you can find yourself delaying writing it precisely because any pinning down of specifics will be a reduction of the grand idea: no concrete rendering can be as all-encompassing and full of vague potential as an abstract idea. It'll be something real rather than just an idea, of course, but it'll also mean relinquishing the sense of possibility that the idea carries with it. You can wind up stuck with an idea about a story indefinitely.

Trying to write it can cure you of the disease before it really sets in, but only if you're willing and able to identify when a story isn't working and ditch it. If you're trying to write an idea about a story and you don't realise that's the problem, you can find yourself enmeshed in a horrible tangle of cobwebs. Pointless-feeling scenes, hollow emotions, padding and general dullness beckon. Everything feels thin and unmemorable. Plots wander about looking lost. You get stuck because there's nothing really there, not enough to build on and not enough for the characters to do - or at best, nothing that can build to a satisfying conclusion. Possibly you have what seems like a good beginning or a good end, but no sense of an overall structure, no destination. The longer you struggle, the harder it becomes to just toss the whole mess and start over.

Ideas for a story are ideas you know you can make something of. They can be wildly exciting, plans unfurling and setting off new plans and everything exploding in your head like fireworks. They can be practical but undramatic; Stephen King describes it very precisely in Misery when he says you feel like a carpenter looking at a piece of wood that might do the job. (Can't get my hands on the exact quote, sorry.) The point is, they're ideas that link on to other ideas or the possibility of other ideas: they point a path rather than dangling mirage-like in the air. They're planks of wood rather than boxes of sawdust.

...to describe the kind of person who's very brave about bearing up under the pain of others? Or a slang phrase?

And if not, is there one in German? The language that gave us schadenfreude (happiness at the misfortune of others) and scheissenbedaurn (regret at things not turning out as badly as you'd hoped) really ought to have a word for this.

And failing that, can anyone suggest one?