Telling, not showing
The brilliant decision in making the new Star Wars ComicCon reel was this: J.J. Abrams could have chosen to wow the audience with special effects, to show a little more, to try to pique interest by satisfying the tension felt by the true fans who don't know what's coming, and can't stand not knowing.
Instead, of following the conventional wisdom and showing, he told. He told a story of care, of excitement, of anticipation.
He created tension instead of relieving it.
This takes resolve and guts. Most of the time, we want to blurt out the answer. But the thing is, people rarely get excited about blurts.