Ben Federman, owner of 1saleaday.com, sells everything from electronics to jewelry to kids' merchandise. But everything he sells has one thing in common: It's a great deal. "Once you build up your clientele," says Federman, "you can buy larger volumes, and that's where you really get the savings. We buy so many of whatever we're selling that we're able to buy at ridiculously low prices and sell at up to 90% off suggested retail."

But it's more than just great deals that keeps his customers coming back for more. Federman's company has earned a loyal following with a strong commitment to their customers that shows in everything they do, including free shipping and a no-questions-asked return policy. Their quality control department ensures the company—and their customers—can feel confident in the products they're shipping out the door. "We don't even bother with items that aren't brand name and that don't come directly from manufacturers or from authorized direct distributors."

A self-professed gadget geek, Federman feels one of the secrets to successful selling on eBay is doing the research and having a feel for what excites people. "Once you know your customers and they know you, it's almost like you want the same type of item that they want. When I'm excited about a product, I'm pretty sure my customer is going to be as well."

Federman's advice for making the most of the holiday buying season is simple: "Plan ahead and be prepared." But adopting some of his company's practices is just good business all year round.