I've always been quite at home with the arrondissement numbering system, with its cute spiraling snail twirling out from the centre. But if you've never really been able to grasp it, or would prefer a rather more sociological take on things, then maybe this map will help you. I found it on the internet from who knows where. The way you do.
Paris If You Don't Please
I'll try to decipher/translate it as best I know how, without recourse to any help whatsoever, I assure you (can't be bothered); I'll just give it to you straight. There is no judgement on my part (that comes later). This is basically what it says about the make up of each of the districts.
1st -Tourists and Dodgy guys from the suburbs
2nd -Clothes and stuff
3rd/11th/20th - one big amorphous blob of trendy young new moneyed casuals - the bourgeois bohemians
6th/7th -Show-off snobs
8th -Tourists and even dodgier suburban troublemakers
Parents -Parents and Relatives Ploucs -Country Bumpkins
That reminds me of those other maps that did the rounds a while ago - the ones slapping similar stereotypes onto whole countries and even the world and it had quite a bit of success if I remember rightly. In fact, it was: the world or bits of it as seen by each nationality, something like that. Here's a sample:
The World as seen by the USA
And just in case you want more, here's another sample. There's a whole calendar's-worth of the things if you have a rummage around... (click for bigger versions, friends).
Europe seen by the British
Europe seen by the USA (left), and by the French (right)
Aren't you glad, like I am, that you don't succumb to such gross oversimplification and downright disrespect. Where do they get these things? Utter nonsense, the lot of it, don't you think ;-)