Decoding Pride and Prejudice

What do you mean I'm sarcastic?

How do we decode sarcasm and satire? Verbally, teenagers use a sarcastic tone of voice. But in Jane Austen's writing, we have to read between the lines, look for exaggerated or understated words, and notice words that are redundant or stick out in some way. Then we assume we can read the sentence as ironic: saying one thing but meaning quite the opposite.

Which speakers use sarcasm or satire the most? The narrator? Elizabeth? Darcy? Mr Bennet? Caroline Bingley? Probably not Jane, who is too sincere and sweet to roll her eyes at anything.

Who 'gets' the satire best? The reader? Darcy? Elizabeth? Mr Bennet? Not Sir Lucas. Not Mrs. Bennet.

Let's try decoding the first sentence of the novel:
"It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife." (Austen 1)
What words are give-aways that this says the opposite of what is really meant? Who is the speaker? Adopting whose point of view? How does the first sentence signal to readers how the book is to be read?