those thanks than you take pains to thank me: if it had been painful, I would not have come.

He's expecting a woman with a crush, she's her normal sarcastic self, and the audience is amused at the wordplay between them. Because her response subverts his expectations, it's even funnier.

Beatrice is the center for many of the humorous parts of the play. For example, in an exchange with a messenger, she says:

Messenger: I see, lady, the gentleman is not in your books.

Beatrice: No; and if he were, I would burn my study.

Though she and Benedick have issues between them, she doesn't actually hate him outright. She's dramatic and says things in a way to amuse people. It's one of the reasons why she's seen as a bitter old maid—people don't appreciate her humor.

Another amusing scene is at the end of the play when Hero reveals herself to Claudio. Shakespeare writes:

Claudio: Give me your hand: before this holy friar. I am your husband, if you like of me.

Hero: And when I lived, I was your other wife.

She unmasks herself.

Hero: And when you loved, you were my other husband.

Hero's family faked her death while they worked to prove her innocence. Her father pretends that she is his niece and makes Claudio promise to marry her before he can see her face. This is amusing to the audience because Claudio and Hero have been kept apart by the machinations of others. Claudio is delighted and Hero is redeemed in his eyes when these schemes are exposed and the lovers are reunited.

This is a bit of a broad question, but I think if you are after the finest comedy in this excellent play, you need look no further than the interactions between Benedick and Beatrice and the kind of verbal dexterity that characterises their "merry war" as each makes clear the disdain that they feel for the other. Consider, for example, the following exchange from Act I scene 1. In response to Benedick stating that he "loves none," note how Beatrice responds:

A dear happiness to women. They would else have been troubled with a pernicious suitor. I thank God and my cold blood I am of your humour for that. I had rather hear my dog bark at a crow than a man swear he loves me.

To which Benedick responds that he would that God keeps her in this frame of mind so that some poor gentleman will escape "a predestinate scratched face." The wit and humour in such exchanges are by far the finest examples of comedy in the play, and are worthy of serious analysis. You might also like to look at the scenes containing Dogberry and how his stupidity and propensity to use malapropisms yields a different kind of comedy.