By using paradoxical and equivocal language, Shakespeare creates an eerie mood right from the start.  The statement "fair is foul and foul is fair" (1,1,11) sets the scene for the play, in that not everything is as it appears.  Macbeth's first lines "So foul and fair a day I have not seen," (1, 3, 38)  are a parallel to how things are in the play.  (e.g.. Lady Macbeth starts off foul then turns somewhat fair, Macbeth starts off fair then turns foul.)

    The witches are one of the main devises used by Shakespeare to set the mood.  The witches begin right away with prophecies for Macbeth.
                "All hail, Macbeth! hail to thee, Thane of Cawdor!"  (1, 3, 58)
                "All hail, Macbeth! that shalt be king here after."  (1, 3, 59)
Macbeth is freaked out that the witches know who he is, and that he is Thane of Glamis.  He takes the prophecies lightly.  At this point he is not ready to take extra action to make the prophecies come true.

    The witches then give prophecies to Banquo to further the mood.
                "Lesser than Macbeth, and greater."    (1, 3, 65)
                      "Not so happy, yet happier."   (1, 3, 66)
                      "Thou shalt get kings, though thou be none:"  (1, 3, 67)
These statements may be confusing at first but they start to come together as the play progresses.  Banquo is lesser than Macbeth in that Macbeth is a king and Banquo is only a thane.  But greater as far a nobility is concerned.  Macbeth is never happy after he kills Duncan.  Banquo is not so happy because he suspects Macbeth but he is still happier than Macbeth.

    The porter scene is used as comic relief for the audience, but many paradoxical and equivocal statements reveal what has happened and what will happen.
                "If a man were porter of hell-gate, he should have old turning the key."   (2, 3, 1-2)
                "Who's there, i' the name of Beelzebub?"  (2, 3, 3-4)
                "Faith, here's an equivocator, that could swear in both the scales against either scale; who committed     treason enough for God's sake, yet could not equivocate to heaven:"  (2, 3, 8-11)
The porter is pretending to be the porter of hell, not knowing the evil that make Macbeth's castle much like hell.

    By now Macbeth is trying to change his fate.  He goes to the witches for more prophecies to try and give himself some more confidence.  The witches prophecies are again in paradox and equivocal language and are in the form of apparitions.  An armed Head, a bloody Child, and a child crowned, with a tree in hand.
                  "Macbeth! Macbeth! Macbeth! Beware Macduff:
                         Beware the Thane of Fife.  Dismiss me.  Enough."
This apparition causes Macbeth to fear Macduff, but the next two apparitions give him confidence.  They trick him into thinking he is unstoppable.
The second apparition is a scary sight for the audience.  A bloody child.  This would advance the mood further by creating an atmosphere of blood and gore.
                     "Be bloody, bold, and resolute; laugh to scorn
                           The power of man, for none of woman born
                          Shall harm Macbeth."
    Macbeth takes this as good news, thinking no one will be able to defeat him.  In the end of the play we find out that Macduff, who Macbeth is warned about, was born by a cesarean section, therefore is not "of woman born"
    The third apparition is a child crowned, with a tree in his hand.
                   "Be lion-mettl'd, proud, and take no care
                           Who chafes, who frets, or where conspirers are:
                           Macbeth shall never vanquish'd be until
                           Great Birnam Wood to high Dunsinane Hill
                           Shall come against him."
    The witches make Macbeth think he is invisible.  They pretty much say don't worry just have fun, be bad, do what you want.

    The mood in Macbeth is created using several effective techniques.  Paradox and equivocal statement help progress the mood but making people think.  While they may be able to see some things through props and acting, Shakespeare lets the audience use their mind to create a scene unique to themselves.