As Norman checks Marion into her room, he tells her about the stationery with the motel name on it, using the same dialogue from Psycho (1960).
When Marion looks up at the house she sees a silhouette in the window, which is a reference to Psycho (1960).
When Marion is eating her sandwich, she tells Norman that her aunt used to say that ladies eat like birds. In Psycho (1960), Norman tells her she eats like a bird.
When Marion notices his taxidermy, Norman replies that he likes stuffing things - another reference to Psycho (1960).