What makes groups successful and what gets them stuck?

There was a gentleman in the 80's (Meredith Belbin) who discovered the Apollo Syndrome. His discovery was broken down into a couple of key concepts. Your group will be successful with the absence of highly dominant individuals and a leader that can hold their own, but not dominate. Also, the leader would need to be skeptical of anyone in the group who "had an agenda" because the "deadly embrace" would happen. "Deadly embrace" came from the computer world when computers with competing agendas in a network would stop each other from making progress.