Poe wanted to write a story in which one man lures another into the underground catacombs and leaves him to die in chains. The only thing that could lure such a man deep underground would be wine. It seems impossible to think of anything else that Montresor could have claimed to have to show Fortunato down there under his palazzo. It had to be some exceptionally good wine. It couldn't be Italian wine because too much of that was available in the city. (Note that at the end of the third paragraph, Montresor writes: "I was skilful in the Italian vintages myself, and bought largely whenever I could." This shows that he cannot pretend to need a second opinion on a cask of Italian wine.) It couldn't be French wine for the same reason. Montresor is French himself. The only other possibility was Spanish wine. Poe may have known very little about Amontillado except that it was the best wine produced in Spain and their most expensive export.
Poe knew it wasn't enough to have a small amount of Amontillado. Montresor claims to have a pipe containing 126 gallons--and furthermore, and most importantly, he claims to have gotten it at a bargain price. It is the bargain price that lures Fortunato underground, not the desire to drink a glass of gourmet Spanish sherry. Montresor knew that Fortunato would not go with him just to taste his wine. The Amontillado (if it existed) would have come into port recently aboard a ship from Barcelona. Fortunato could have found the ship with ease and tasted the Amontillado on board-which Montresor would have done himself if the wine had been real and the ship had been real. Montresor pretends to be in a big hurry to get an expert opinion on his pipe of nonexistent imported Amontillado and says he is on his way to Luchesi. Fortunato only goes with Montresor to prevent him from going to Luchesi, who would also be extremely interested in a cargo of wine at a bargain price.
Montresor seeks revenge on Fortunato, for a "thousand injuries" and a nameless insult. His plan involves burying Fortunato alive, deep within the catacombs of the Montresors. So he devises a plan to bring Fortunato to his own death. He tells Fortunato that he has purchased a cask of Amontillado, and needs Fortunato's expertise to determine the quality.
He flatters Fortunato, continually appealing to his sense of pride. He also decieved Fortunato, telling him that he will ask another appraiser instead. Fortunato is lured by this flattery, & by his competition with Luchesi (the other connoisseur). He is also drawn by the promise of Amontillado, which is a very rare dry sherry. Fortunato has already been drinking and celebrating during carnival, and he is easily convinced.
However, once he agrees to follow, Montresor continues his plan to ensure his revenge will work. He opens a bottle of wine and pauses often in their walk, to toast Fortunato. Yet his real intention is to make Fortunato even more intoxicated, thereby rendering him helpless and vulnerable. Although Fortunato is normally a respected citizen, when drunk he lives up to the jester costume which he is wearing. His weakness for alcohol allows him to be led deeper and deeper into the catacombs, eventually reaching his burial place.
The answer to this question can be found in the first few paragraphs of the text itself. If you read it closely, you learn right off the bat that Montresor is angry with Fortunado because of the "thousands of insults" that Fortunado had sent his way. Because of this, Montresor has devised "revenge...with impunity." But, in order to exact his revenge, he must lure Fortunado down into the catacombs. This is much easier than it might seem. First of all, it is carnival, a huge party in the city, and Fortunado is already a bit tipsy from celebrating and drinking. Secondly, Montresor knows that Fortunado "prided himself on his connoisseur-ship in wine," and this was quite a big weakness for him. Fortunado thought he was an expert of wine, and whether one wine was better than another or not. So, Montresor devises a plan. He decides that he will pretend that he just bought a bottle of a fine wine, called Amontillado, and that he wants Fortunado to taste it and tell him if it really is a good wine, or if he paid too much for it. This of course would require that they go into the catacombs. Montresor knew that would appeal to Fortunado's sense of pride over his "expertise." Montresor is even sneaky enough to lead Fortunado into thinking that tasting the wine was his own idea. The conversation goes, in part, as follows:
"I was silly enough to pay the full Amontillado price without consulting you in the matter. You were not to be found, and I was fearful of losing a bargain...As you are engaged, I am on my way to Luchesi. If any one has a critical turn it is he. He will tell me—”
“Luchesi cannot tell Amontillado from Sherry.”
“And yet some fools will have it that his taste is a match for your own.”
“Come, let us go.”
“To your vaults.”
“My friend, no; I will not impose upon your good nature. I perceive you have an engagement. Luchesi—”
“I have no engagement;—come.”
So, Montresor is able to lure him down to the vaults on the pretense of having a cask of Amontillado that he was going to bring to someone else to taste to see if it was any good. Fortunado would not have that! HE was the best wine-taster, so HE must do it.
I hope that those thoughts helped a bit; good luck!
Montresor appeals to Fortunato's ego. Fortunato prides himself on his skills as a connoisseur of fine wine. Montresor tells Fortunato that he has been given a cask of Amontillado, a very rare and expensive wine, but that he believes it to be fake. Montresor tells Fortunato he is going to find Luchresi, another expert on wine, and ask him if the wine is truly Amantillado. This is too much for Fortunato to take, and he tells Montresor that he will come and taste the wine and give his expert opinion. Fortunato is already drunk; Montressor gives him additional wine on the way to the Amontillado, therefore it is not difficult for Montresor to shackle Fortunato and build the brick wall around him.
At the carnival, Montresor takes advantage of the fact that Fortunato is already a bit drunk to trick him into the catacombs. He appeals to Fortunato's ego and refined taste for wine, telling him that he had just purchased a fine bottle of Amontillado and wanted him to taste it to make sure he had not paid too much. He claimed they had to go into the catacombs to do so, thus luring Fortunato to his doom.