Over the years, as teams have grown more diverse, dispersed, digital, and dynamic, collaboration has become more complex. But though teams face new challenges, their success still depends on a core set of fundamentals. As J. Richard Hackman, who began researching teams in the 1970s, discovered, what matters most isn't the personalities or behavior of the team members; it's whether a team has a compelling direction, a strong structure, and a supportive context. In their own research, Haas and Mortensen have found that teams need those three "enabling conditions" now more than ever. But their work also revealed that today's teams are especially prone to two corrosive problems: "us versus them" thinking and incomplete information. Overcoming those pitfalls requires a new enabling condition: a shared mindset. This article details what team leaders should do to establish the four foundations for success. For instance, to promote a shared mindset, leaders should foster a common identity and common understanding among team members, with techniques such as "structured unstructured time." The authors also describe how to evaluate a team's effectiveness, providing an assessment leaders can take to see what's working and where there's room for improvement.