Here's an example:
Marge stood at the edge of the canyon, ready to end her life on the count of three. Last year she'd had nothing but wonderful adventures ahead of her--glamorous parties, trips to any place in the world. Her mom and she lived together then, and her mom didn't approve of that kind of lifestyle. She always shook her head when Marge came down the stairs dressed for an evening out or a trip to Paris. What did her dowdy mother know? Nothing. Neither did her dad. He never did much except read the sports pages.
Huh? Just look at the poor reader who thought she was getting into something really exciting. She was promised this count of three, a girl hurling herself off the cliff to sure death, and then suddenly she's back to a year before, discussing Mom and Dad. Maybe this backstory can come later, but not now, not on this first page. On the first page the writer has to maintain the intensity she's established with that opening line.
It took a while for me to decide what was gimmicky rather than intense, interesting and fresh. So here's what I came up with to test the openings I write. I ask myself these questions:
1) What does that line do to start developing the character?
2) What does it do to show the reader something about the narrator?
3) How about the setting? Does it take the reader where my story will happen?
4) Does it help to establish the tone of my story?
5) And, of course, does the paragraph that follows sustain my first line? How about the rest of the page? The chapter?
One line can't do all of these things, but I think it should do at least one and do it well. Note that the categories are for discussion and convenience and not always clear-cut, especially when the writer is skilled and can pack a lot into a few words. One thing that I really like to accomplish is to reveal any of these four story elements and jolt the reader at the same time with the unexpected, the tantalizing, the bizarre.
Okay, so I want something that will keep eyes on my writing, that will get the reader to move on to my first paragraph (where, of course, I still must shine as a writer), and then to the bottom of that first page where I'll make them turn to page two with a brilliant "what's next" sentence. So, you see what I'm saying? The first line is very important, but you can't hang everything on it even when it's the most fabulous first line ever written.
Here are a few first lines I admire. I've tried to separate them out according to the categories I use--again for discussion and convenience. And you'll notice I don't stick with YA and MG; I don't stick with the most recent books either.
"The first time I saw him he couldn't have been more than sixteen years old a little ferret of a kid, sharp and quick." Schulberg, What Makes Sammy Run?
"The first thing I did was steal a body." Lester, Bedeviled
"I planned my death carefully; unlike my life, which meandered along from one thing to another despite my feeble attempts to control it." Atwood, Lady Oracle
"If I'd blinked, I would have missed it." Henry, Learning to Swim
"She saw a beach made of ice, and she felt her heart breaking." Lo, Huntress
"When he woke in the woods in the dark and the cold of the night he'd reached out to touch the child sleeping beside him." McCarthy, The Road
"On rainy days, we don't have to work in the woods, gathering water until our backs ache and our fingers tremble around out spoons." Bachorz, Drought
"Ten minutes before it happened, four-year-old Laurie Kenyon was sitting cross-legged on the floor of the den rearranging the furniture in her dollhouse." Clark, All Around the Town