What Is an Effective Team?
As a leader, it will be your responsibility to develop teams. In project management, this is especially important since you'll depend on your teams to accomplish the project goals. Read this resource on leadership, teams, and project management and consider the idea of "reliable promises" to create effective teams.
Managing Transitions
High performing teams develop a rhythm. They have a way of working together that's hard to quantify and that is more than just a series of carefully implemented techniques. Once you have the pleasure of working on a team like that, you'll begin to recognize this rhythm in action and you'll learn to value it. Unfortunately, you might also experience the disequilibrium that results from a change in personnel.
Endless books and articles have been written on the topic of change management, with a focus on helping people deal with new roles and personalities. Your Human Resources department probably has many resources to recommend. Really, the whole discipline comes down to, as you might expect with all forms of team management, good communication and sincere efforts to build trust among team members.