Defining and validating system requirements are one of the most important activities in the development of an information system. It often requires collaboration of multiple stakeholders who have different needs and perspectives. In many cases it is especially challenging to facilitate the gathering of the requirements in an efficient and effective manner in a hierarchical environment and yet encourage system stakeholders to freely share their ideas and opinions. The goal of our research was to implement and evaluate a collaboration engineering process that would facilitate system requirements validation and elicit new requirements from key stakeholders who had disparate needs. We applied several collaboration "thinkLets" in our process and then evaluated their effectiveness. The study focused on a User Alerts/Events Notification system for the US Military at USSTRATCOM. Two sessions were conducted that generated a number of insights on the implementation and transferability of thinkLets as well as lessons learned by novice facilitators.