Peer assessment (PA) is widely implemented in higher education, and it can play an important role in online learning by connecting students to their peers and enabling feedback from multiple sources. However, high-quality feedback is not guaranteed. And students tend not to use peer feedback. Preparing for, designing, and implementing PA can be challenging for instructors, especially those who are relatively new to online teaching. This paper proposes guidelines for preparing for, designing, and implementing PA based on a review of empirical studies. The paper first reviews the benefits of PA, the important role that PA can play in online courses, and the need for effective preparation, design, and implementation of PA activities in online courses. Afterwards, based on a review of empirical studies that aim to improve the effectiveness of technology-facilitated PA interventions, the paper proposes guidelines for PA activities.