I did the restaurant thing, from dishwasher to manager and every job in between; server, bartender, chef, oh my. I had a soft sell technique. Don't care for intrusive and unimaginative hard sell as a consumer, so won't do it as a point of sale client either. Nope, one of my few never say nevers, which goes to show as a never say never itself I don't lightly say never, including never not saying never.
Anyway, an anecdote. A customer, who I suspected of being a covert company shopper evaluating my job performance, said, "You're not upselling, make me wonder if you're a good salesperson and why you're in this line of work."
"And by your appearance and expressed expectations, I expect you're the kind of customer who already knows exactly what you want."
"Oh, I do, do I?" Maybe you could tell me what to order."
"I'd recommend the most expensive item on the menu because it's what I like most and no one has ever been disappointed, but you'll order the least expensive because it's our signature item."
He did. Then sent it back saying it was a disappointment. I replaced it with my recommendation. He was satisified and putty in my hands after that, asking my recommendations on dessert and beverages. He seemed the sort to take offense to any alcohol discussion, so it was strictly soft drinks. At bill paying time, he said I was a great if deviously subtle salesperson, entertaining, and a credit to the organization.
It took about a month for the shopper's report to wind its way through channels. The kitchen took a hit. The front of the house passed muster.
My experiences with bookstores are about the same, selling- and consumer-wise. Libraries, wow, two kinds of librarians, ones who take the same satisfaction I do from personably serving consumers' needs and those who don't.
Spread the love of written word.