In this complex, fast-changing job market, just putting in the hours and being good at what you do may not be enough. You need an edge. And the surest one these days is to possess the skills that are most in demand in your field, that help your employer keep up with the technological, economic, and social forces that are transforming so many industries. The key, of course, is to know exactly what those skills are, how to get them, and what the payoff will be.