What are three incidents that reveal Pip as a truthful storyteller?Great Expectations by Charles Dickens

That Pip's comments about his experiences are veritable is
later evinced in the narrative by things that characters say and
do. 

Pip's experiences with Uncle
Pumblechook

Early in the novel,
Pumblechook partakes of Christmas dinner with the Gargerys; while there the pompous man
makes a toast after  instructing Pip repeatedly to be "grateful, boy, to them which
brought you up by hand."  From these early experiences, Pip perceives that Uncle
Pumblechook is "the basest of swindlers."  On the day before he is to go the Miss
Havisham's in order to play with Estella, Pip is transported to Pumblechook's store
where he observes early in the next morning that the corn chandler is petty and watches
the other merchants to see who conducts more business than
he: 

Mr.
Pumblechook appeared to conduct his business by looking across the street at the
saddler, who appeared to transact his business by keeping his eye
on the coach-maker....

Later
in the narrative, after Pip becomes apprenticed to Joe and Miss Havisham gives Pip a
"premium," Pumblechook congratulates Pip, telling him "I wish you joy of the
money!"  Then, when they go to the town hall, Pumblechook pushes Pip before him as
though he is directly involved in the ceremony of
apprenticeship. 

Further,Pip's depiction of Pumblechook as
a hypocritical man who fawns before those who are wealthy such as Miss Havisham because
he believes that money makes people more worthy than others proves to be accurate in
Chapter XIX in which he flatters Pip now that he is a gentleman instead of browbeating
him as he has done earlier.  In Chapter XXII when Pip stops into the tavern at the Blue
Boar and is shown a newspaper in which Pumblechook records
himself

as the
Mentor of our young Telemachus,....the founder of the latter's
fortunes.... 

Here
Pumblechook's attempt to elevate himself is, perhaps, the greatest evidence of the truth
of Pip's charge of the corn chandler's
hypocrisy.

Pip's encounters with the
relatives of Miss Havisham

As a boy, when
Pip is called back to Miss Havisham's on her birthday, he notices sitting around the
decaying wedding cake table, three ladies and one gentleman who appear to be "waiting
someone's pleasure"; these people Pip describes as "toadies and humbugs."  As they await
Miss Havisham's "pleasure," they gossip about Matthew Pocket who has not come for his
relative's birthday.  The most talkative of these is Camilla who, though she utters
repeatedly the exclamation "Poor dear soul!" about Matthew, stifles a yawn.  Joining
in is Sarah Pocket, wife of Matthew.

As evidence of this
superciliousness, Pip's visit to the Pocket home demonstrates how Sarah Pocket ignores
her children and as she is engrossed in a book of titles.  Even when the baby's life is
threatened by Mrs. Pocket's handing it the nutcracker and the maid has to rescue it, the
woman continues to discuss the importance of names and social class while the other
children "tumble" everywhere.

Pip's
evaluations of Estella's cruelty and
coldness

When Pip first plays cards with
Estella, she ridicules his coarse hands and boots, as well as his calling the knaves
"jacks."   Pip's later recordings of Estella's coldness--"her calm face was like a
statue's"--prove to be true when Pip later visits Miss Havisham who is desolated by
Estella's lack of affection: "to be proud and hard to me!"  
Estella replies coldly, "I am what you have made me."