A trigger sentence compels a reader to read more. It is the hook that causes us to give the author an opportunity to impress us. The old "...it was a dark and stormy night" from many years ago was a great trigger sentence in its day...but its day has changed. Today we, or more accurately, our readers, are inundated with fast moving visuals, over the top sound and constantly evolving one upmanship but the task for an author is still the same - write a compelling first sentence that will invite the reader to keep going.
In my workshops and coaching, I often use examples from bestselling books to illustrate this point and encourage ( some might say, bully) authors into creating better trigger sentences. In a weekend magazine, I came across a couple of good examples of trigger sentences that make you want to read more or even just simply, buy the book.
Chris Anderson is the editor-in-chief of Wired magazine and one would assume, a geek of the highest order but he can sure create a trigger sentence: "There's no getting around it. Gelatin comes from flesh and bones. It's the translucent, glutinous substance that skims to the top when you boil meat."
from FREE: The Future of a Radical Price by Chris Anderson
So, tell me, given the book's title, did you expect that sentence to start it, do you want to read more of it? Of course you do. And, that is your job as an author, to create a hook that will cause the same curiosity in your readers. That's how every chapter in your book should begin - with a trigger sentence.