When students get to us they don't, usually, understand how to work in a group. There are assigned roles with individual responsibilities and expectations. There are also expected behaviors of each member of the group and behaviors by the entire group.
Last year we came across a Ted Talk by Tom Wujec where he described a challenge (presented by Peter Skillman). This is now, famously, known as the Spaghetti Challenge. Here is a great video to show what a typical classroom is like in the last few minutes of this challenge.
The rules are simple and we like to present the challenge as an engineering design brief (got to get the vocabulary started too). During the first day of class they are given the challenge. The next day we introduce roles and the students break up into expert groups based upon their roles. The roles are Designer, Tester, and Builder. Therefore the expert groups are the Design Team, the Test Team, and the Build Team. Before the expert groups get started we reflect on what we observed the previous day. What went well? What hurdles needed to be overcome? What frustrations did they feel? And other thoughts as they come up. We then ask how we could make the experience better.
On the third day the expert groups have a quick meeting and then the students are sent back to their original groups to make the tower. The groups are reminded that each person in the group has a role and they are not to do anything that isn't specifically related to their role. Once the challenge is completed we take measurements but instead of a "winner", based upon height, we recognize groups that worked well together. We take time to talk, again, about what worked and what frustrations were felt.
By the end of these three days, the students have learned most of the other students' names and (more importantly) I know many of the students' names. They have also worked in groups where no one is assigned as the "group leader." Each of them has had an important role that was needed for all of the group to be successful. Finally, they have seen what group relationships worked and what relationships were not as effective.