The order of adjectives

From Mark Forsyth, in his book The Elements of Eloquence:

Adjectives in English absolutely have to be in this order: opinion-size-age-shape-colour-origin-material-purpose Noun. So you can have a lovely little old rectangular green French silver whittling knife. But if you mess with that word order in the slightest you’ll sound like a maniac. It’s an odd thing that every English speaker uses that list, but almost none of us could write it out.

Of course, there are exceptions, all of which he explains here, but it's a good little lesson to remember.