This toolkit has been designed by the Research and Evaluation Unit (RIMU) at Auckland Council to be useful to those wishing to improve public programmes or services, policy development, or team decision-making. It draws on a range of existing resources produced by the Behavioural Insights Team, the OECD and others (see ‘other resources’ on the next page). This toolkit has two components that can be used either separately or together. The first component is a step-by-step process for developing a behavioural intervention. It guides the user through understanding existing behaviours, identifying a desired behaviour, brainstorming ideas for promoting the desired behaviour, and robustly testing the best ideas. The user should follow the steps in the order they are numbered. It is focused on key questions to ask at each step. It is not a complete guide to how to answer these questions, however, and the user may need to rely on other research and evaluation resources to help with each step. The second component of the toolkit is a series of ‘brainstorming’ cards. The cards cover many important behavioural principles to keep in mind when looking to improve programmes, policies, or decision-making. Each card includes a description of the behavioural principle, some examples, and suggestions for how to apply the principle. They can be used on their own or to brainstorm ideas as in the step-by-step process above. To help with navigation, the card set has been organised into a series for better services and a series for better decisionmaking, although there is overlap in the use of the cards. The former is marked with a red dot in the top left corner and the latter with a green dot.