I’m going to let you in on a secret: You have to be nice to your customers if you want to keep them. Not just ‘send-them-the-occasional-email’ nice, or ‘ignore-them-until-their-birthday’ nice — genuinely nice. New customer nice. For some reason, we’ve got things a little backward in the marketing world right now. Instead of giving the best deals to the people that keep our businesses going, we tend to give the best deals to people who don’t....