Many cities across Europe and elsewhere are exploring new ways of bringing together diverse actors and stakeholders, and enabling collective action across all sectors of society. In this document, NetZeroCities outline one crucial part of doing this, namely setting up a Transition Team, which brings together the municipality and the ecosystem of multiple actors across society. There is no single blueprint for achieving this; each city will need to work in ways that best accelerate progress in its specific context. However, there are some insights and lessons learnt that can be shared and built upon, and this document makes a series of suggestions.