With increasing diversity of media, more-powerful consumers, greater demand for return on investment (ROI) accountability, and a tsunami of data, marketing mix models are becoming essential tools to optimize budget allocation and campaign execution. This report surveyed 30 experienced modelers on the management, use, and supporting practices that enable an effective marketing optimization strategy. Marketing leaders should read this report to compare themselves with more-mature practices and to identify the next stage of evolution they must embrace to master a data-driven optimization approach.