Donors spend billions of dollars on development research each year, but what is the impact on policy? This Briefing Paper summarises ODI’s work on understanding how policy processes operate in the real world, as part of its mandate to inspire and inform policy and practice that lead to the reduction of poverty. The paper presents six key lessons that are essential to any researcher or organisation wishing to generate evidence-based policy change, and an eight-step approach for policy entrepreneurs wishing to maximise the impact of research on policy. This is known as the RAPID Outcome Mapping Approach (ROMA).