The verdant hills of Ireland
A pathetic drunk
A loud-mouthed frat boy
A privileged white dude...
In these cases the adjective adds information we already associate with the rest of the noun phrase. So we think of the hills of Ireland as being green, drunks as being pathetic, etc... We call this the epithet, and in Spanish, in these cases, we put the adjective before the noun.
I find this use unsettling, because we can smuggle in a judgment simply with an adjective. If I say "a screaming infant" or a "callow youth," I am making a judgment about an entire category.
The other uses of the adjective is to distinguish part of the class of nouns from other parts. So I if I said:
"Contemporary Egyptians knows little about the ancient Egyptians" the adjective is serving that purpose. In Spanish we put that kind of adjective after the verb. We know this is different because we can omit the epithet and the meaning of the sentence doesn't really change:
"How I remember the verdant hills of Ireland"
"How I remember the hills of Ireland"
"You are a drunk!"
"You are a pathetic drunk!"
But if the adjective fulfills the function of distinguishing the meaning is not preserved if the adjective is omitted:
"I was married to a stingy man" // *"I was married to a man" //. *"The Egyptians know little of the Egyptians."
There is a technique in which the poet will put one adjective before and one after: "rugosa piel inmóvil" (Vicente Aleixandre). Both adjectives are descriptive, and don't really differ in their function all that much. It is more of a literary flourish.