Know what your subject thinks, wants to destroy, wants more of. Editors are important. Henderson said it's like a game with him to know every single fact. Grehl had mentioned he had had an omelet the day of the shooting. Readers want those details.
Place is also important.
Henderson went to the cemetery in Chicago where Tony Williams was buried. He found the graveyard. One of the key scenes in the story is when Aaron Williams is talking to his mother about his brother Tony while Henderson listens, in the Chicago apartment. The writer fades from the scene, and it is only Aaron talking to his mother. Short sentences and simple thoughts are good.