If you want to work as a team you must set some common goals. Where are you going together?
The environment must be collaborative where everyone has a say and their voice is heard.
Each person must have a team first attitude. This means the success of the team is more important than the individual success. The individual must sacrifice at times for a greater team reward.
The tone must be set by the leaders and everyone else will buy in. Nothing is in the dark. Everyone must be radically truthful and have radical transparency.
With everything in the open, there is a trust and encouragement for everyone to be the best they can be.