A second important factor is cross-team communication. Common requirements, similar issues, shared data, and reusable functionality all should be openly discussed and coordinated. A third factor is the insistence on the part of the top team leadership that individual and sub-team successes be innertwined. Consistent deliverable, quality assurance, methodological, and review standards must apply to all team members equally. It becomes a reflection of everyone involved, radiating confidence and certainty if spirits are high, seething with doubts and confusion when direction is lacking.
Leadership certainly plays a vital role, but individual team member attitudes make the difference.
Hopefully, each person's work will mesh with the rest of the group's results. This will probably happen if everyone clearly and precisely understands the ultimate phase objectives. This is where human nature begins to step in and things can begin to get interesting. Unique and potentially conflicting agendas take shape. Before you know it everyone is busily working away and the atmosphere appears to be productive.