After add-drop period, I put students into groups of five. If one is sick, they can call a home-group member to come pick up their paper and so on. They are encouraged to use each other in any constructive way possible. I often remind them that their goal is to help each other toward excellence. Each group is assigned a number or name.
Every group turns in a sheet with the names and phone numbers of each member.
At the beginning of each class, students get in their home groups to exchange ungraded papers. It is important to have them sit together, in circles if possible. Increasingly, I see this as an important component of this method. Each group is given a manila envelope into which they put all ungraded papers for their group. Each paper has the last four digits of the student's Social Security number.