Describe briefly how act 3, scene 3 prepares the audience for the climax of the trial scene?

Act III, scene iii of The Merchant of Venice is relatively short, but it is still significant, nonetheless, especially in how it prepares us for the trial scene. Shylock is presented here as a rather vindictive character, hell-bent on having his pound of flesh. Antonio, for his part, is relatively calm and stoical, accepting of his fate (at least, he is after he begs Shylock for mercy and realizes that he's getting nowhere).
Shakespeare's negative portrayal of Shylock in this scene prepares us for his comeuppance in the trial scene. At various points in the play, Shylock has come across as a sympathetic character, the victim of hypocrisy and anti-Semitic prejudice. Yet here, Shylock's vindictiveness and refusal to yield undercut any sympathy we may have felt toward him. It seems that, in this scene, Shakespeare's setting up Shylock to be taught a valuable lesson on the quality of mercy.