Most spa clients appreciate the quality and cache of designer purses, shoes and clothing. So it's not surprising that this same clientele is often intrigued by designer facials—those signature treatments at high-profile spas that not only offer effective elements that result in healthy, luminous skin, but also boast a clever name, marketing hook and a long list of celebrity devotees. We call these iconic treatments "cult facials." But you don't have to have a Beverly Hills address (nor the prices to match) to develop your own unique skincare treatments. Here's an insider's look at what these cult facials offer, and some expert strategies for capitalizing on their unique "hooks" and creating signature, headline-making services at your own day spa. —Alison Singh Gee