As my favorite shops are used bookstores, I will develop that as an example.
Since habits formed early are likely to last, it's important to focus on a youth market. University students are a particularly appropriate segment as they are likely to need to buy textbooks and may be persuaded to buy other books if they can be attracted into the bookstore.
First, as a display strategy, I would organize a display of select heavily discount books and games that are best sellers in the college market between the door and the textbook section so that students interested in buying textbooks would walk by other books they would be likely to buy.
Next, I would create a "buy 2 textbooks, get a 50% discount on selected paperbacks" promotion, and advertise it in nearby university newspaper and via e-mail to teaching assistants, I would also offer 10% additional discounts on every 3rd book purchased to students or professors who maintained links to the bookstore on their personal websites or Facebook pages.