They can also set the mood right away. Take the first line of 'The Catcher in the Rye' by J.D. Salinger: 'If you really want to hear about it, the first thing you'll probably want to know is where I was born, and what my lousy childhood was like, and how my parents were occupied and all before they had me, and all that David Copperfield kind of crap, but I don't feel like going into it, if you want to know the truth.' This line gives a sense of the narrator's voice, which is cynical and a bit rebellious, and draws the reader into his world.
Some great first lines introduce a key concept or theme. Consider the opening of 'The Lord of the Rings' by J.R.R. Tolkien: 'When Mr. Bilbo Baggins of Bag End announced that he would shortly be celebrating his eleventy - first birthday with a party of special magnificence, there was much talk and excitement in Hobbiton.' This line starts with a celebration but quickly leads into a much larger adventure and a world full of magic and danger.
Great first lines often present something unexpected or thought - provoking. For example, the first line in 'Moby - Dick' by Herman Melville: 'Call me Ishmael.' It's simple yet mysterious, making the reader wonder who Ishmael is and what his story will be.
They create mystery. For example, like in the first line of 'The Great Gatsby' - 'In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.' It makes you wonder what that advice was and why it has stayed with the narrator for so long.
They create intrigue. For example, if the first line is 'She found a letter in the attic, addressed to a stranger but filled with words of love.', it makes the reader wonder who the letter is from and who the stranger is. This mystery draws the reader in.
They create mystery. For example, like the first line in 'The Hunger Games'. A cold bed makes you wonder what happened, and this mystery makes you keep reading to find out. Simple as that.
They create mystery. For example, a line like 'In a dark, forgotten corner of the old house, something stirred.' makes the reader wonder what that something is. It's simple yet effective in making the reader want to know more.
They often create intrigue. For example, a first line that poses a question or presents a mystery makes the reader want to find out more. If it starts with something like 'She saw him across the crowded room, but she knew there was something different about him that she couldn't quite put her finger on...' It makes you wonder what that difference is and how it will play into the love story.
They create mystery. For example, the first line of '1984' by George Orwell, 'It was a bright cold day in April, and the clocks were striking thirteen.' The oddity of the clocks striking thirteen makes you want to read on to find out more about this strange world.
They create mystery. Take 'All children, except one, grow up' from 'Peter Pan'. It makes you wonder which child didn't grow up and why. This mystery makes the reader keep reading to find out.
They create mystery. For instance, a first line like 'She was found dead in the attic, but no one knew how she got there.' It makes the reader want to find out what happened. Mystery drives the reader to keep reading to solve the puzzle.
They often introduce an emotional state. Such as 'She was broken - hearted, but then he came along like a ray of hope.' It makes the reader care about the character's emotional journey.
They create mystery. For example, a line like 'The letter arrived on a Tuesday, but it was the contents that would change everything.' makes the reader wonder what's in the letter and how it will change things. It's a simple yet effective way to pique curiosity.