This is a broad-ranging discussion of the role of economics and economists in the formation of government policies. The focus is on helping economists who wish to be influential in the policy process. The paper covers rationales for and against economist involvement in the policy process (market failure, government failure, economist failure), a range of theories that attempt to explain aspects of the policy process, and practical advice and insights based on the experiences of policy economists. Many challenges are highlighted, but some clear opportunities are apparent, particularly through explicit advocacy for the public interest.