How does Shakespeare introduce the absent Macbeth?in Act 1

In Shakespeare's Macbeth, the character Macbeth actually isn't physically introduced until scene 3.  In scene 3, he and Banquo simply walk in on the three witches just as they finish a charm.  Macbeth comments on the weather using the same words spoken by the witches at the close of scene 1 (which of course in some way, depending on one's interpretaion, connects Macbeth to the witches):  "So foul and fair a day I have not seen."  Banquo then notices the witches, and the scene takes its course.

Macbeth's name is mentioned in scene 1, by the witches, when they reveal that the three will meet again when they meet with Macbeth, and again in scene 2 when King Duncan gives Macbeth credit for the military victory over Cawdor.  These mentions of the character prepare the audience for Macbeth's appearance in scene 3.