Concerns about the negative effect of social media on well-being have generated much interest around the development of social media interventions, which aim to change users' interactions with social media to improve well-being. To aid the effective study and design of such interventions, we introduce a new theoretical approach, guided by self-determination theory. We review current interventions and categorize them by the context in which they intervene: social media platforms, devices, users, families and society. Drawing on established behavioural change models, we then evaluate how social media use affects the core psychological needs of autonomy, competence and relatedness. We propose theoretically grounded design features that can be applied to maximize the effectiveness of future interventions. In response to the increasing calls for interventions to counteract social media risks, our recommendations will inform future research in academia and industry, with practical applications to enhance well-being in this digital age.