How does Hamlet's father manipulate Hamlet even when he is dead?

The fact that Prince Hamlet's father returns from the dead
as a ghost to tell his son what happened to him is the basis of the entire play.  Hamlet
respected his father in life, and wants to do right by him in death, and that is what is
central to most of the actions of Hamlet for the rest of the
play. 

Even before the ghost speaks he is manipulating
people.  He is appearing to guards and friends of Hamlet, but not speaking so as to get
them to tell Hamlet about this strange thing -- a ghost.  By having his friends all say
they saw a ghost will make Hamlet more likely to believe what he sees and not think it
is merely a hallucination caused by grief.

Once the ghost
is actually talking to Hamlet he says several things to manipulate Hamlet into
completing his request for vengeance.  First of all he starts talking, in kind of scary
generalities about where he is in the afterlife -- it is purgatory where he is "doomed
for a certain term to walk the night, And for day confined to fast in fires."  This
creates a certain amount of sympathy in Hamlet for the horrible afterlife his father is
suffering.  After that is established, he kind of draws out the suspense of his
message.  First he mentions that he was murdered, then he tells how, and finally
he delivers the fateful news, that "the serpent who did sting thy father's life now
wears his crown."  By building up the story this way it is manipulating Hamlet's
attention and making the last note the most powerful and
shocking.

The next phase of manipulation goes on for
several lines when the ghost provides the more specific and gross details of his death,
thus manipulating Hamlet's sympathy and anger.  He also makes several negative
statements about Claudius's seduction of Gertrude and how Claudius is such a lesser man
than he.  This feeds right into how Hamlet already feels about the gross, incestuous
marriage of his mother to Claudius and how he has already expressed his displeasure at
the kind of man Claudius is.  In a sense, Hamlet is very prepared to hear awful things
about Claudius -- he thought those very things even before he learned that Claudius
murdered his father.

The ghost also manipluates Hamlet by
drawing a sympathetic picture of Gertrude so that Hamlet won't try to punish her for her
action in marrying Claudius.  Claudius is the only one that the ghost wants revenge on. 
He tells Hamlet to leave his mother to heaven's
judgment.

His final manipulation is to the command to
"remember me."  He wants Hamlet to have at the forefront of his thoughts the father that
Hamlet used to be and the facts that he learned today.  Together, all of that should
keep Hamlet highly motivated to avenge his father's death by taking care of Claudius
once and for all.