Due to expected benefits such as citizen participation and innovation, the release of Public Sector Information as open data is getting increased attention on various levels of government. However, currently data release by governments is still novel and there is little experience and knowledge thus far about its benefits, costs and barriers. This is compounded by a lack of understanding about how internal processes influence data release. Our aim in this paper is to get a better understanding of these processes and how they influence data release, i.e., to find determinants for the release of public sector information. For this purpose, we conducted workshops, interviews, questionnaires, desk research and practice based cases in the education program of our university, involving six local public sector organizations. We find that the way data is stored, the way data is obtained and the way data is used by a department are crucial indicators for open data release. We conclude with the lessons learned based on our research findings. These findings are: we should take a nuanced approach towards data release, avoid releasing data for its own sake, and take small incremental steps to explore data release.