Effective teams are highly interdependent. The goal is clearly defined by the team, and team members are willing to contribute their best to achieving the target. Supportive, honest and open communication creates an environment where team success can be evaluated without blaming an individual. Roles are defined. Risks are taken.
Leadership is shared.
Conflict is embraced as a necessary step to improvement. Keep teams together for more than one project. Spend the time needed to do team building exercises aimed at developing team trust. Discuss strategies for dealing with team conflict. Design projects that assign defined roles that require specific talents and skills.