Character mistake: The newspaper clipping about the Hannibal/Will encounter in the pre-credits sequence states that it could be described as a "the beginning of sorted mystery", as opposed to a "sordid mystery." (00:09:06)
Character mistake: At the very beginning of the film, when Hannibal Lecter is serving dinner to his guests, one diner asks "what is this divine looking amuse-bouche" when she and the other guests have a full plate of food. An amuse-bouche is a single bite of food meant to be served at the beginning of a meal, not a plate full of food. Lecter's guests would be better educated.
Character mistake: During the opening credits, one of the newspaper headlines reads "FBI Agent in Extremely Critical Condition". The story under the headline says that "local police found Dr. Hannibal Lecter fatally wounded in his Chandler Square residence", and that "the call was made by Special Agent Will Graham of the FBI". Neither was true since Lecter lived and Graham went unconscious after the stabbing.
Answer: His choices had to do with the layout of peoples' property. At his job, he studied customers' family video tapes that contained scenes of their homes and yards. He looked for seclusion around the properties, easy-access back entrances, whether there was a family dog that would bark, and so on.
raywest ★
But what was his reason for killing them? Was it because he saw a happy family and he was angry because he never had one or because he saw a life that he would never have?
He chose the houses that had big backyards. During the Edward Norton/Lecter interaction, Lector says something about how blood looks in the moonlight.