Not only do you have to nail the first line, you also have to have some staying power to keep them reading.
Cheryl Klein likens it to falling in love. You see a person across the way and are intrigued – that’s the cover. You inquire about them and learn a little more, or read the flap copy. You invest a little time in them to see if a relationship is possible. With a book, you read the first chapter and either fall in love or disengage.
In Second Sight: An Editor’s Talks on Writing, Revising, and Publishing Books fro Children and Young Adults, Klein discusses rules of engagement. There first must be voice, the soul of the book, the foundation upon which the whole novel is built. The narrative voice must be that of a person the reader is interested in. Readers don’t have to like the person, just be fascinated by them. She offers tactics to build that intrigue through voice.
She says your character must be real, their behavior anchored in real human psychology and behavior. This applies even to fantasy or books with animal narrators. They must take action. The story should start with the MC driving the action or responding to circumstances they find themselves in. The opening should be surprising or strive for mystery. Try to pique the reader with questions that can only be answered by reading further. The ultimate goal of the first chapter is to hook the reader with intrigue about a character they are interested in.
It just so happens that Writer’s Digest posted an article with tips for starting a novel at the same time I’m seriously trying to rewrite my NaNo piece. I read the article, followed the links then purchased the download.
James Scott Bell had an article in the January issue. He says you need to create a doorway of no return for you MC by the first fifth of the book. Local author Ann Dee Ellis, at a WIFYR workshop a few years back, first introduced me to this idea. Ann Dee says there must be a change that prompts the novel. Something must happen, either to your protagonist or by them, so that their world is different. Bell calls it a disturbance you create for your character that will force him into the conflict/confrontation central to the plot.
So to have your reader fall in love at first sight, provide them with intrigue and a reason to care about your main character. For a lasting relationship, send the MC through a door of no return.