This report provides Mayors and other policymakers with a policy framework and diagnostic tools to anticipate and implement strategies that can prevent their cities from locking into irreversible physical and social structures. At the core of the policy framework are the three main dimensions of urban development. * Planning -- Making land transactions easier, and making land use regulations more responsive to emerging needs, especially when coordinating land use planning with infrastructure, natural resource management, and risks from hazards; * Connecting -- Making a city's markets (for labor, goods, and services) more accessible to neighbourhoods in the city and to other cities. Here the focus is also on investing in public transport and pricing private transport fully; * Financing -- Enabling a city to leverage its own assets to finance new assets, for example, through land value capture; establishing creditworthiness for local governments and utilities so they can access domestic debt and bond markets; and setting clear and consistent rules to attract private investors to create jobs in cities. This report also distils lessons from prototypes of urbanisation diagnostics which reflect challenges for countries at nascent (Uganda, Vietnam), intermediate (China, India, Indonesia), and mature (Brazil, Colombia, South Korea, Turkey) urbanisation. These diagnostics under the World Bank's Urbanization Review programme have engaged strategic counterparts, such as those in national ministries of finance and planning, in thinking about policy choices that influence urbanisation and city development.