Hook your readers in the first 3 seconds or else. If you’re first sentence doesn’t intrigue your reader, they will stop reading. It’s that simple. However, creating that coveted first sentence is very hard.
If you are writing nonfiction, that first sentence should be assertive and daunting. It should make your readers think, “I’ve been doing it wrong my whole life.” or “I need to know more about this.” If the first sentence is as common as anything that can be read on the internet and not cause a second thought, why should your reader continue? Your hook should be thought provoking. It should be bold, exciting, contradictory, stimulating, and/or convicting.
If you are writing fiction, that first sentence needs to instill emotion in the reader. Begin in an action scene or with inner conflict of an interesting character. You have to compel your reader to feel. Whether they should be feeling anger, fear, sadness, love, joy, surprise, anxiety, envy, panic, pride, relief, or sympathy…the point is to make them feel it with your writing.
The best advice I can give you about how to cultivate this iconic sentence is to write it last. Write the rest of your book, no matter what is, and then go back and craft the best hook possible based on everything your book represents. Also remember, the point is not only to hook your readers in the beginning but to keep them hooked throughout the story. You have to keep up that same momentum throughout your book if you’re going to keep your readers reading.