Here's a rule that most of us never think about.
It goes like this. When you describe something in English you first of all describe how many of them there are. Then you describe the thing's quality (that's what you think of it: nice, nasty, or peculiar, for example). Then its size, age, shape, colour, origin (a country, perhaps) and lastly purpose.
People don't usually use all of these categories to describe any one thing, but it can be done: three wicked big old knobbly red Kentish spell-casting witches.*
If you use only a few adjectives then the order above is still used: for instance, number still comes before shape in six fat celebrities, and size comes before colour in enormous green bogies.
As far as I know you can't go wrong with that rule, though of course sometimes you can choose not to follow it. For instance a little old lady (which follows the rule) is an old lady of no more than average height who presents little apparent threat to anyone; but an old, little lady will be very small indeed.
Unfortunately the rule doesn't cover all words. Slimy, for instance. A big slimy old slug or a big old slimy slug or a slimy big old slug?
All I can say is that between them they've eaten half my garden.
Words that describe things are called adjectives, as it happens, but please don't be alarmed: I mean, you've been using them nearly all your life and one's never bitten you yet.
Word To Use Today: a string of nice juicy adjectives. The word adjective comes from the Latin word adjicere, which means to throw to.
* Not that Kentish witches are especially wicked, of course.