This chapter proposes to identify the skills and attributes policy actors need to be successful in their roles and to explore how policy-making expertise develops over the course of their careers. The chapter presents the limited literature dealing with this topic and discusses the results of an empirical study directed at identifying the kinds of skills and attributes policy actors regard as crucial to their role. As policy actors gain years in the job, the skill sets and attributes they value move away from those skills that can be learnt towards cognitive expertise and judgement and intellectual openness. The chapter points to the importance of cognitive skills and judgement, interpersonal skills, and intellectual openness. It also explores how policy actors-both politicians and bureaucrats-engaged in policy roles learn their craft; how this expertise develops over time; and how it relates to individual performance.