Agile methodologies build on selforganized teams: they organize and manage themselves in a high performing way.
Successful teams need to
- be diverse
- be stable
- be cross-functional
- trust each other
- have a good conflict and failure culture
- commit to their common goal
- take accountability
- focus on team results
To become a real high performing team, teams have to grow.
For example, have a look on the Teambuilding stages by Bruce Tuckman:
Forming -> Storming -> Norming -> Performing (-> Adjourning)
Another interesting model is Richard Hackman’s work on High Performance Teams. Google it out.