Word-of-mouth marketing—using viral e-mails, sample distribution and buzz factor—is taking off. Follow these principles to get the most out of your word-of-mouth campaign: 1. Be interesting. Before you run an ad, before you launch a product, ask your spouse about it. Trust me, if he or she finds it interesting, you’ve got a winner. 2. Make people happy by creating amazing products. Go the extra mile and provide excellent service. Make sure the work you do gets people energized, excited and eager to tell a friend. 3. Earn trust and respect from your customers. Be good to them. Talk to them. Honor their intelligence.