In what ways does Montresor manipulate Fortunato? What weaknesses does Montresor exploit?

Fortunado manipulates him by playing on his (Fortunado's) knowledge of wine. He prays on Fortunado's vanity when it comes to his expertise of wine. Fortunado suffers from the weakness of excess pride and vanity when it comes to wine.

Montresor tells Fortunato about how he bought something that was supposedly "Amontillado", but that he wasn't sure about it. He knew how much Fortunato prided himself for his knowledge of wine.