Feed-in tariffs (FITs) are the most widely used renewable energy policy in the world for driving accelerating renewable energy (RE) deployment, accounting for a greater share of RE development than either tax incentives or renewable portfolio standard (RPS) policies. FITs have generated significant RE deployment, helping bring the countries that have implemented them successfully to the forefront of the global RE industry. In the European Union (EU), FIT policies have led to the deployment of more than 15,000 MW of solar photovoltaic (PV) power and more than 55,000 MW of wind power between 2000 and the end of 2009. In total, FITs are responsible for approximately 75% of global PV and 45% of global wind deployment. Countries such as Germany, in particular, have demonstrated that FITs can be used as a powerful policy tool to drive RE deployment and help meet combined energy security and emissions reductions objectives. This policymaker's guide provides a detailed analysis of FIT policy design and implementation and identifies a set of best practices that have been effective at quickly stimulating the deployment of large amounts of RE generation. Although the discussion is aimed primarily at decision makers who have decided that a FIT policy best suits their needs, exploration of FIT policies can also help inform a choice among alternative renewable energy policies.