Point of View
Objective…But Not Totally Omniscient
All these movies are called Harry Potter and [Insert something weird or mysterious], so it's only right that we stick primarily with Harry's perspective. Most of what we know or see, we get by following him around—and we don't usually know more than he does.
There are exceptions, of course: such as when we see the face of the guy who sends up the Dark Mark at the Quidditch World Cup (whereas Harry and his friends don't), and we also see Karkaroff sneak into the room with the Goblet of Fire unbeknownst to, well, everyone else. Mostly, though, we're limited to the world according to Harry, which definitely helps keep the mystery and suspense factors high.