Subject Matter
The subjects available to literary journalists, like the subjects available to conventional feature writers, are all but boundless. Ted Conover says in his foreword to True Stories, "You think of a story that seems to need telling, and you go where it's happening: a living room, a railroad yard, a street, a high school, a doctor's office, Peru."
I think of literary journalists as seeking out interesting events, interesting people, interesting places, interesting occupations, interesting situations. The world, to put it tritely, is their oyster.
Technique
1A) The use of the first person is common in literary journalism.
1B) The writer's voice is often heard in literary journalism even if the writer uses the third person exclusively.
2A) Literary journalism is based on a considerable amount of research.
2B) The practitioner of literary journalism immerses himself or herself in the subject at hand, spending hours, weeks, sometimes months doing legwork.
3A) The literary journalist often writes in scenes, much as a fiction writer writes in scenes.
3B) The scenes often include detailed description.
3C) The scenes often include dialog.
3D) The scenes often focus on interesting characters.
4) The literary journalist often includes a considerable amount of exposition and background based on 2A and 2B.