The numbers of sessional staff teaching in law schools continue to grow, yet little has been done to provide for their professional development. This is particularly critical because these colleagues are likely to be less able to attend face-to-face development sessions or to participate in informal ‘corridor’ discussions. This article analyses what amounts to best practice in professional development of sessional colleagues in an online environment, including: the need to adopt a peer-to-peer tone; appeal to a range of teacher experience; draw on contemporary scholarly approaches to teaching and learning issues; and provide recognition of digital literacy, internationalisation, diversity, gender and Indigenous issues. These insights are drawn from the experience of developing modules as part of the Australian Government funded Smart Casual: Promoting Excellence in Sessional Teaching in Law project. The article draws on feedback from sessional staff focus groups and an autoethnography of the authors of the modules to reflect on the complexity of the task of developing professional development materials that neither patronise nor alienate their target audiences and the implications this reflection has on the importance of collegiality in the law school environment.