In nonfiction, the opening sentence generally points the reader to the subject under discussion directly in a matter-of-fact style.
[1] Techniques to hold the reader's attention include keeping the opening sentence to the point, showing attitude, shocking, and being controversial.
Formulaic openings are generally avoided, but expected in certain genres, such as fairy tales beginning "Once upon a time...".
Inspired by the opening, "It was a dark and stormy night...", the annual tongue-in-cheek Bulwer-Lytton Fiction Contest invites entrants to compose "the opening sentence of the worst of all possible novels",[5] and its derivative, the Lyttle Lytton Contest, for its equivalent in brevity.
The opening sentence may sometimes be also used as the title for the work; the Latin for this is incipit, meaning 'the first part' or 'the beginning'.