That faint sound of grinding gears that you hear is retailers ramping up for the holiday season (yes, I know it's not even Halloween yet, but that's not going to stop the creeping holiday-ism from spreading). I've spent the last 15 holiday seasons on the sales floor of a bookstore, and I've learned a few things: 1) don't go for the leopard-trimmed santa hat unless you can pull it off, 2)it ain't Christmas if Eartha Kitt ain't singing "Santa Baby," and 3) people always wait till the last minute and are therefore desperate for you to suggest books for them to buy.
Now, we've all got our favorites, but the key to handselling on the sales floor is listening, not talking. You need to cater your responses to the needs of the customer; Max Brooks's World War Z might be the best book you've ever read, but if the last book your customer read was by Nicholas Sparks, then a zombie book just isn't going to cut it, no matter how awesome it is. So you need to ask some questions: What kind of books do you like? Who's your favorite author? Is this book a gift for someone else?
It seems obvious, but you'd be surprised how many sales opportunities are missed because the clerk doesn't take the time to find out what the customer really wants.