Before the catchy first line there's (sometimes) an epigraph. I went to the library yesterday and came home with a bag o' books. Some adult, some YA. Each of the adult novels had an epigraph, but not one of the YAs did. I've wondered about this before--why are they used less often in children's literature?
Lest someone launch into a comment about the pomposity of epigraphs, I'll disclose right now that I've got epigraphs in two of my novels (the epigraphs were also used for the titles). The first was in Come in From the Cold, for which I lifted Joni Mitchell lyrics (and earned a place on her official [fan-run] website!) and the second is in Too Big a Storm, for which I used a line from Margaret Wise Brown's wonderful The Sailor Dog.
There is something about epigraphs, of course, that says "In Case you don't get what this is all about, here's a big fat hint."