According to Ron Ricci and Carl Wiese, authors of the book,
The Collaboration Imperative, high-performing teams have the following characteristics:
People have solid and deep trust in each other and in the team's purpose--they feel free to express feelings and ideas.
Everybody is working toward the same goals.
Team members are clear on how to work together and how to accomplish tasks.
Everyone understands both team and individual performance goals and knows what is expected.
Team members actively diffuse tension and friction in a relaxed and informal atmosphere.
The team engages in extensive discussion, and everyone gets a chance to contribute--even the introverts.
Disagreement is viewed as a good thing and conflicts are managed. Criticism is constructive and is oriented toward problem solving and removing obstacles.
The team makes decisions when there is natural agreement--in the cases where agreement is elusive, a decision is made by the team lead or executive sponsor, after which little second-guessing occurs.
Each team member carries his or her own weight and respects the team processes and other members.
The leadership of the team shirts from time to time, as appropriate, to drive results. No individual members are more important than the team.