First, Montresor must hide his feelings of hatred for Fortunato. He does this so successfully that throughout the entire plan, and even at the end, Fortunato has no clue that Montresor wants to kill him.
Second, Montresor chooses Carnival time to enact his plan; this guarantees that Fortunato will not be immediately missed, buying Montresor some time if he needs it. Brilliant.
Third, Montresor must be able to bring Fortunato to his empty house. To do that, he does the simplest and most clever thing he can think of to do during Carnival time
