I wrote
a blog post about openings last month, where I talked about using a defining moment to keep the reader's interest. Here are some examples from that post--
Well, you could start by setting up a problem:
"My name was Salmon, like the fish; first name Susie. I was fourteen when I was murdered on December 6, 1973.
~ The Lovely Bones by Alice Sebold
Holy crap! Murdered? I'd say that's a problem.
Or raise a question:
"There was a boy called Eustace Clarence Scrubb, and he almost deserved it."
~The Voyage of the Dawn Treader by C. S. Lewis
What? What did he do to deserve it? Was he always a naughty child, or did he recently do something very bad? I must know!
Or introduce a WTF? moment.
“When your mama was the geek, my dreamlets,” Papa would say, “she made the nipping off of noggins such a crystal mystery that the hens themselves yearned toward her, waltzing around her, hypnotized with longing.”
~Geek Love by Katherine Dunn
Uh, WTF? I'm going to keep reading to figure out exactly how the mother came to be a geek, and what that has to do with the title.
The thing is, the rest of your story has to live up to this "moment", so don't let your opening write a check the rest of your manuscript can't cash.
I'm with others, though-- don't stress until the first draft is finished, because the opening chapter will probably wind up with more changes to it than the entire rest of the novel. You say you know how it ends? Try to think of a way to use what you know about the ending to write an opening scene.
There's been a ton of great advice in this thread. Hope it helps you!
