Language affects how we see things, and few things give a faster impression of an imaginary world than slang. If you're setting your story in your home town during the present day, then you'll have a handle on its way of speaking, but if you're setting it in a future dystopia, imaginary world or fictional sect, then a question arises: how do these people speak?

Anyone who wants to make up slang should begin by reading Anthony Burgess's A Clockwork Orange, a book heavily laced with an imaginary slang referred to as 'nadsat talk', 'nadsat' meaning teenager. Burgess pulls off an almost impossible feat by creating something close to an alternative language.

Let's look at the opening passage, which immediately lays out what Burgess is going to do:

'What's it going to be then, eh?'
There was me, that is Alex, and my three droogs, that is Pete, Georgie and Dim, Dim being really dim, and we sat in the Korova Milkbar making up our rassoodocks what to do with the evening, a flip dark chill winter bastard though dry. The Korova bar was a milk-plus mesto, and you may, O my brothers, have forgotten what these mestos were like, things changing so skorry these days and everybody very quick to forget, newspapers not being read much neither.

You can tell several things at once. The use of ordinary English, such as 'newspapers not being read much neither', tells you Alex's accent straight off: this is a working-class boy, probably Cockney but definitely not posh, given his double negative. (Malcolm McDowell plays him with a slight Northern accent in the film.) Similarly, 'O my brothers', a phrase Alex is fond of, gives you a sense of tone: Alex is joking, a bit, he's conspiratorial and having some fun with the register; we can hear the playfulness of his delivery. Neatly, Burgess sketches this in, so we can hear Alex's voice speaking, which greatly lessens the risk of reader alienation by all those odd words he's using.

But actually, the words aren't that odd. A Clockwork Orange is very carefully written, and one of the important things is that with unfamiliar words, you can almost always work out what they mean by context. (On the rare occasions when you can't, Alex obliges with a translation - 'Pete had a rooker (a hand, that is)', for instance.) If you look at the words in the paragraph I'm quoting, they're all fairly clear. Alex is sitting with his three 'droogs' in a bar, and he refers to them all by nicknames or diminutives, so presumably 'droog' means friend or companion. 'Making up our rassoodocks what to do': 'rassoodocks' obviously means minds, as it's in the middle of a common expression. 'Flip' could mean a number of things, but it's either a term of criticism or an emphasiser, and in either case it's plain that he's complaining about the weather; 'mesto' might mean bar, but as he's already told us that the Korova is a bar it's more likely that it means place or establishment, either would fit; and from the context, obviously 'skorry' means quickly.

Burgess doesn't need to give translations for any of these words. What Alex's freewheeling use of them does is forces us into collaboration with him: we have to learn his language if we want to understand what he's talking about, and once we've learned his language, we're looking at things through his eyes. And that has an impact later. No one word has quite the same emotional tone as another, even if they're describing the same thing, and when Alex describes the appalling things he does, his joky, unsympathetic lingo splits our sympathies in a fascinating way. If somebody tells you they hit an old man, then it's hard to feel anything but condemnation, but if they 'tolchocked' and old 'veck', then it somehow doesn't sound as bad. We have Alex's judgement and our own jostling for position inside our heads. The result is twofold: it makes Alex's crime spree much more bearable to read about, and it gives us an outstanding sense of Alex's personality. We may not like him, but we definitely understand how he thinks.

Now, if you're looking to invent your own slang, you don't need to go as far as Burgess. There are points, though, where a bit of slang is helpful. When I was writing Bareback, for instance, it occurred to me that some slang might be necessary, given that the only words available to me for things like werewolves were heavily associated with horror movies, and that wasn't the tone I was aiming for. Either I could use words that had the wrong feel, which in effect meant words that didn't mean what I wanted them to mean, or I could make up my own - so I made up my own. The best way to do most kinds of writing is to use instinct, as instinct packs in a lot more subconscious information than processed thought, but there are some basic rules you can extrapolate from those instincts. Here they are:

1. Don't use a slang word where you don't need one. That will sound artificial. If you listen to the way people talk, there's really not much slang in it unless they're affirming a strong group identity; they tend to use a lot of ordinary words.

2. Think about the context in which slang is used. Unless we're talking about a really deep slang that's intended to confuse outsiders or impress insiders, the words that get slanged tend to be subjects where people get a little uncomfortable: sex, bodily functions, death, minorities and money. Either that, or it's a specialist's jargon, involving words that the speakers use more often than most people.

3. Slang words have to be useable; there's no point at all having a slang word that's harder to say than the word it replaces, because slang is supposed to be casual, not effortful. A hard-to-use slang word doesn't catch on. Even Cockney rhyming slang quickly shortened most of its phrases: 'use your loaf', not 'use your loaf of bread' (head); 'cobblers' not 'cobblers awls' (balls); 'berk' rather than 'berkley hunt' (which I'm not translating in case there are children in the audience).

4. Unless a word is funny, of course. Slang is often ludic (playful), and will keep a phrase if it's entertaining. But it had better be fun to say. Humour is one of the main ways in which people express their world views, so ludic slang can tell you a lot about a speaker's attitude. We don't mock the things we respect; you wouldn't expect seminary students to refer to God as 'Old Beardy', for example, but they might refer to the tiresome old fidget who always sits in the front pew and tries to correct their sermons as an 'altar-nibbler'. If they did develop slang words for God, it would be playing on their respect for him: 'I'm feeling tempted, so I'd better have a word with Himself and ask for guidance.' The joke would, in effect, be directed back at themselves, rather than at God.

5. Broadly speaking, in fact, all slang expresses the attitude of the person using it. It might be playful, or defiant, or cynical, or boastful, but whatever it is, the register has to suit the speaker.

6. Slang has to come from somewhere; you can't just make up a word. Frequently it mangles a word from another language, the way Burgess bastardises Russian - 'chav', to take a recently popular word, is adopted from Romani. Sometimes it's an adaptation of words already existing in the language - 'greenback' for dollar bill is the first example that comes to mind. Possibly it's an abbreviation - 'sov' for sovereign. In any case, slang is almost never pulled out of the air.

7. Slang usually comes in with words in common usage. There's no need to have a slang word for, say, 'metaphysical', firstly because most people say it so seldom that between the first time you say it and the second, you'll have forgotten what the new slang word was, and secondly because the circumstances in which you say it pretty much never call for a jocular, slangy tone. The convenience of this is that slang words can do a lot of work. If the word 'dubbon' means 'variegated holly leaf', it probably is not going to have a strong presence in the novel, but if it means 'man', then it'll get used a lot, giving the whole novel a slangy feel without having to invent three hundred new words.

8. Slang generally has some kind of internal consistency. Even English, a language that got invaded several times and then strapped on its boots and invaded everyone else, has a general ambience; languages have their own harmony. Hence, words will have a similar feel. For fun, let's see if you can sort the following random slang words into two separate categories:

Prigger
Mozzie
Bilk
Nubbing ken
Yabber
Dinkum

(I'll give you a clue because I'm nice: one is Australian English, the other is thieves' cant. To help you even more, here's a link to a site about thieves' cant, because it's an incredibly rich and expressive language, which gives you a real feel of a culture as well as lots of interesting words, and is well worth studying if you're planning on creating slang of your own. But no peeking till you've done the test, right?)

9. If in doubt, keep it simple. A few well-chosen words here and there give a much stronger impression of a culture than a mishmash; I remember a cooking teacher telling me that a few flavours in a dish is tasty, but too many and it gets bland, and the same rule applies here.

Any thoughts, anyone?