Kelly Armstrong has done it more than 40 times. I suppose we should give her a listen.
It’s a promise that says “If you like this, stick around… and if you don’t, maybe this isn’t the book for you.” To achieve that, your first scene should reflect the tone of your story (dark or light, fast-paced or leisurely.) It should also demonstrate the point of view and tense (first-person, third-person, past tense, present tense etc.) Try to establish the genre as well (literary, mystery, science fiction or fantasy, et cetera). A reader who is enjoying an opening chapter that seems to be a romantic comedy will not be pleased if they later realize they’re actually reading a dark thriller.
Bookninja 