Reaching out to passive job seekers is a key part of any recruiting strategy, experts say. And it's not the easiest. After all, unlike workers actively applying for jobs, passive job seekers aren't hanging out on Monster.com and other career boards. They're generally productive and happy at their current jobs. Still, "if you can strike a chord with someone who seems truly happy, but you notice the one thing that could be better, then you have a unique hook to capitalize on," said Jen Warne, director of recruiting at global professional services firm Towers Perrin.