Structure is not an aspect of film that is often praised. Yet in a suspense, mystery or horror film, it's vital. Not just that the story itself be interesting, but that it be presented in a way that obscures exactly what is going on while keeping the viewer interested.
One of the major challenges to a ghost or monster film is how to build the tension without giving too much away. When should the terrifying entity be shown, and how can it be presented in such a way that it's not disappointing. Very often films fall down when that thing that's been chasing everyone around is suddenly revealed to be a giant carrot, or a dwarf in a rubber suit.
The Ring does this perfectly. The tension increases throughout the film, leading to many great, chilling moments. There are three "shock" moments in the film, but they are buttressed with enormous amounts of tension-building subtlety. The mystery is complex and strange, and the investigation is extraordinarily well handled. We glimpse pieces of the ghost's sad and terrible history even as we see the horrifying effects it has on the world around it. The Ring's story manages to push so many buttons; the images of a child along in a sterile medical environment, cruelty to animals, an isolated community, technophobia, medical testing, the hints that home is not as pleasant as we want it to be.
The structure of the film, the way the audience gets hints about what's going on, works beautifully. There is no Basil Exposition telling us what happened. The viewer, like the characters, piece what's going on from interviews, observations, and strange experiences. We get glimpses of frightening consequences without knowing what triggered them, except that there's a videotape involved, and people who watch it die. This lack of clarity gives the story a lot of impetus.
This all comes very terribly clear at the end when we watch what happens when someone watches the videotape we have only seen glimpses of. Who we thought was only the victim turns out to be the tormentor, and she crawls out of the television to do her horrible work. It's a hugely chilling moment, as we look at everything we've learned for the past hour and a half in a different light.