Students find learning to design software challenging. There are often multiple ways to solve a problem, and it is not easy to recognise how well one is doing. Feedback from the lecturer, teaching assistant, or peers may help students learn from their mistakes. In this paper, we study students giving and receiving peer feedback on software design to discover the type of feedback that students find helpful, provide guidance in giving good feedback, and learn how students use the feedback they receive to improve their design. We examine the data from a software project course for third-year informatics bachelor students. We asked students to give peer feedback and respond to the feedback they received. We discovered that students value i) explicit positive feedback, ii) feedback with specific examples, and iii) separate feedback on syntax and semantics. We present guidelines for stimulating helpful peer feedback and found that students’ motivation or seriousness in working with the assignment affects their willingness to incorporate the feedback they received into their design.