In the age of connected customers, organizations are increasingly devoted to social and group marketing. In doing so, firms need to consider not only interactions with customers but also interactions among customers. Such interactions among customers are dynamic in nature and thus create a dynamic structure of influences among customers. This article, using 27 years of data on university alumni donation and event attendance, highlights the importance of the interdependence that arises from joint event attendance among potential customers over time and the substantial effects such interdependence has on behavioral outcomes. Therefore, when designing group marketing strategies and deciding which customers to target, companies need to consider group similarities due to demographics, contacts and interactions among customers over time, and the synergistic effects between customers who interact with each other and also share similar demographics. Accordingly, this article provides guidelines on data collection, design, implementation, tracking, and fine-tuning of group CRM strategies.