Globally, much biodiversity is found on private land. Acting to conserve such biodiversity thus requires the design of policies which influence the decision-making of farmers and foresters. In this paper, we outline the economic characteristics of this problem, before reviewing a number of policy options, such as conservation auctions and conservation easements. We then discuss a number of policy design problems, such as the need for spatial coordination and the choice between paying for outcomes rather than actions, before summarizing what the evidence and theory developed to date tell us about those aspects of biodiversity policy design which need careful attention from policy-makers and environmental regulators.