Describe how Macbeth's character changes throughout the play Macbeth?

In Shakespeare's Macbeth, before
Macbeth kills Duncan, his thoughts are only on achieving the throne for himself.  He
gives no thought to the prediction by the witches that Banquo's heirs shall be king. 
Once he is crowned, though, his own kingship is no longer enough.  His ambition has
deepened and at that point he wants to create a dynasty.  Thus, he orders the murder of
Fleance, Banquo's son, for no other reason than to eliminate Banquo's
heirs.

Macbeth also begins to rely on the witches more
heavily after he kills Duncan and is crowned.  He even initiates contact and seeks them
out in Act. 4.1.  Following his visit to the witches, he becomes even more intent on
maintaining power, throwing almost what could be described as a tantrum when he can't
get Macduff, because Macduff has gone to England.  Macduff slights Macbeth by not
attending his coronation or his feast, and Macbeth pays him back by ordering the
slaughter of Macduff's family.  This overreaction demonstrates Macbeth's loss of
perspective and control as the play continues.

At the same
time, the Macbeth of Act 5 is at once rash and contemplative and philosophical.  One
minute he childishly and maliciously berates a messenger, and the next minute
contemplates human existence and becomes nihilistic.  He psychologically moves back and
forth between believing the witches and knowing their predictions are too good to be
true, and between being willing to fight for his crown and die nobly, and knowing
whatever he does is meaningless anyway.