"It was a dark and stormy night."
"I told the boys to stay quiet while I went to fetch my gun."
"It was little more than three miles from the Wall to the Old Kingdom, but that was enough."
Your first line is everything. I'm not kidding when I say that. This is literally, after the cover and perhaps the back cover, the first thing that the reader will see of your story. It's gotta pop. It's the hook. This is the thing that the reader sees and goes "huh, wait, this is interesting. Let's read more."
The summary can do a lot for bringing a reader in, but the first line is the story. It's the style. It's you. You gotta be able to pull the reader in and say "This is worth reading." It doesn't have to be big and dramatic. A Wrinkle in Time starts off playing with a cliche, and weaves it seamlessly into the story. Yeah, it's a dark and stormy night, and we chuckle seeing this line because it's the starter for every proverbial story. But we keep reading.
What about a bait and switch? Twice Shy does this. Turns out the narrator is a teacher, the boys are his class, and the gun is an airgun, being used for a demonstration. The first line makes us go "wait, what's going on?" and then we keep reading, and it's turned on us, and we laugh. Clever! Well done! It got our attention, but wasn't out of place. And yes, the gun gets fired by the third act, don't worry.
Finally, what about something mysterious? Sabriel promises a different world than we're used to, something strange and mystical. The Wall? The Old Kingdom? Why is three miles enough? We're curious at these tantalizing hints, and we want to know more.
"Oh no!" You think. My first line isn't like that!
DON'T PANIC! You don't have to have your first line be absolutely perfect the first time around. That's what editing is for. It took me three or four tries to get Blue Star's first line to something that would be intriguing and hooking, but still fit. The first time it was good, if a little wordy.
"No one knows why, one fine morning as the express was passing through, Angelica Moore took a stroll off the platform."
A good start, but it gives too much away right off the bat, and it doesn't work with the first scene. My betas didn't really like it, either. So I changed it.
"My cousin Angelica Moore killed herself."
Another good start, but it still didn't work--betas pointed out that the narrator doesn't know this at the start of the story! Dang. They suggested adding stuff ("I just didn't know it yet") but I wanted my first line to be alone. So I tweaked it again.
"I died for a living."
That's good. It gives you some insight into the story but doesn't give too much away, and makes you wonder what's going on. For now, it works. I might end up having to change it again, I don't know. But that's what editing is for.
What's your favorite first line? Why?