Whether your story stops at romantic kisses or goes further with explicit sex, you can score that satisfying physical scene by selling it long before it happens. One way to do this is to first build your case that these two need to be together—even if they don’t know it yet—and then deny them (and readers!) that togetherness. Attack that relationship. Use outside forces to shove the lovers apart when they crave nothing more than togetherness. Use misunderstandings to cause one or both lovers to pull away when readers crave nothing more than togetherness. Trigger the lovers’ fears so that they run away just when readers think they’re about to score togetherness. The anticipation will grow so excruciating that when they final get to hook up, the scene will seem to write itself. At that point, you won’t need to convince anybody of anything.