This guidance document identifies the best options for successful delivery of draft Target 3 of the Global Biodiversity Framework (GBF) from the Convention on Biological Diversity (CBD). There is good evidence that this will radically increase the success of biodiversity conservation. “Success” is measured in ecological, social and economic terms, ideally all three will be met in individual sites, or at least for the system as a whole, but guidance is given on trade-offs where necessary. Discussion is confined to protected areas and other effective area-based conservation measures (OECMs) as recognised by the CBD and the International Union for Conservation of Nature (IUCN). Consideration is given to factors that influence area-based conservation, including drivers and conservation interventions. Thirty per cent is global, rather than automatically applying to each country, and covers 30% of land and inland water, and 30% of coastal and marine. The guidance addresses a range of questions, which together develop a business case for the most effective (particular cost-effective) ways of delivering Target 3 in different situations. Analysis draws on case studies, to identify robust strategies. Whilst hopefully of use to anyone interested in responding to the GBF, this guidance is aimed primarily at CBD signatories implementing draft Target 3, and at donors to assist with funding decisions in implementation of the Target.