“I’m cold,” Draco said in that crisp voice he used when he expected something done about it.
That's the first line from the_con_cept's loopily wonderful reversathon fic, Stalks and Bonds (parody threesome bonding fic, Snape/Harry/Draco). It's a lovely example of what I think is a perfect opening line: starts in the middle of the action, doesn't bother with exposition, tells me worlds about the character and attitude not only of Draco but of the narrative POV-person perceiving Draco's protest, and it's witty in a way that would suit both a humorous story or a dark ironic one. And it's the entire opening paragraph and it's not too long. You want to suck me into a story? Yeah. Do that.
The rest of the story, happily, is just as delightful--with an opening line like that, you know it's likely to be. 'S the nature of writing skill.