My experience is that teams are naturally occurring phenomenon -- that is effective teams. In a word, they essentially create themselves. Or more formally, Self Organize. This occurs 1) whenever there is an issue/task of critical and common concern. 2) The team members essentially self select, and join because they care to. 3) The issue/task itself is so complex that no single person nor small group could even start to get their minds around it. 4) There is a vast diversity of opinion, stakeholders, whatever. 5) High levels of passion and conflict (a sign of passion) surround the issue/task. 6) A sense of urgency exists -- This need to be done NOW!
Given these conditions an effective working team will form. Provided it has the space/time to do so.
Negatives would include: Planning everything. Creating an organizational structure and/or agenda. Attempting to control the process and results. To the extent that any of these negatives occur, the team will perform less than optimally. Given maximum effort at all of the above, it is possible to preclude all possible positive activity. Which is usually experienced as, "One more meeting."
A useful approach for those seeking to enable such effective teams is to start by Thinking of one more thing NOT to do. Such things as -- No preset agenda, no facilitators....
Supportive experience (for myself) includes 30+ years of working with self organizing teams, both naturally occurring (the majority) or artificially induced. Under the latter heading would appear the 350,000+ iterations of Open Space Technology which have occurred (nobody counted) in 146 countries, involving millions of people.
I'll try and keep up here online but a) this is summer in Maine. and b) I am definitely geriatric -- also called slow. If you are in a rush for information you can do the following:
Google my name (Harrison Owen)
Check into: www.openspaceworld.com www.openspaceworld.org
Email me at firstname.lastname@example.org