Why do so many of our get-togethers feel awkward and unproductive? Priya Parker, author of “The Art of Gathering: How We Meet and Why It Matters,” says it’s because most of us don’t know how to transform stuffy events—from conferences to tedious family dinners to office holiday parties—into memorable gatherings full of moments to savor. Parker shares the secrets of being a good host, lessons everyone can learn from Harry and Meghan’s royal wedding, and tips for revolutionizing your next business meeting.