In this poem, death is not personified as something scary like the usual "grim reaper" view of death. Instead, death is shown as a very nice companion -- maybe even a suitor of the woman who is speaking.
Death takes the speaker for a nice carriage ride. He even brings along a chaperone (Immortality). They do not go to anywhere horrible or scary or supernatural. Instead, they just pass by regular sights like a schoolyard. The only thing that is the least bit chilling is that they end up at her new home (it's a grave, but it's not really shown that way).
So Death is personified in a pretty benign way in this poem.
The vision of death offered in Dickinson's poem is more of a companion than anything else. It is seen as a force of comfort, of reverie, and of careful companionship. The construction of death is one where the speaker is able to see examples of life through the company of death. This is not a menacing force that causes pain and separation. Rather, it is one where through company, one is able to view life and view the transitory nature of consciousness. This personification is vastly different than traditional Western visions of death for there is little to either prevent embracing it or to prevent its presence.
The first example of personification within the poem is that death stops for the narrator. This indicates that death has the ability to stop and go and get the person. Death is kindly, a quality associated with a person. Death knows no haste, ability to hurry, but death could only know something if he has a brain and can be cognitive of something. Death and the setting sun are presented as "he" and have the ability to pass by one another.
Emily Dickinson's whole poem presents death as a person who has come to get the narrator who is too busy getting on with her life to stop living. Death arrives on its own and picks her up in a carriage but takes he time to take her past things that she enjoys as he takes her to his place.