No matter what genre, every story needs a good opening. Here are four characteristics* and examples of a good opening:
1. Keeps the reader wondering, what happens next? Like in Shiver, by Maggie Stiefvater: "I remember lying in the snow, a small red spot of warm going cold, surrounded by wolves."
2.Establishes the tone of the piece. "Rage. Sing, O Muse, of the rage of Achilles, of Peleus' son, murderous, mankiller, fated to die, sing of the rage that cost the Achaeans so many good men and sent so many vital, hearty souls down to the dreary House of Death. And while you're at it, O Muse, sing of the rage of the gods themselves..." Dan Simmons' Ilium.
3.Immerses the reader in the physical world of the piece. "The Island of Gont, a single mountain that lifts its peak a mile above the storm-wracked Northeast Sea, is a land famous for wizards." Ursula LeGuin's A Wizard of Earthsea.
4.Introduces the characters and situations. "Clare: It's hard being left behind. I wait for Henry, not knowing where he is, wondering if he's okay. It's hard to be the one who stays." From The Time Traveler's Wife, by Audrey Niffenegger.
* Alice LaPlante/The Making of a Story, p.467