Many factors contribute to a successful project. The following tips should help your group along the way.
Having defined roles within the group is essential. A group leader and a secretary will help define this structure.
Your group doesn't have to, and probably shouldn't, be run as a dictatorship. However, having a leader who can choose between different options and keep an eye on the progress of the other group members is a very good idea. If team members aren't performing, the group leader should be prepared to deal with this. If decisions can't be made by mutual concensus the team leader will have to choose for the group. The leader should maintain a broad familiarity with all the areas of activity in the project. Often the group leader will be responsible for integrating the other members contributions.
The group secretary is responsible for maintaining the documentation of the project. This includes the three reports and logbooks. This doesn't mean the secretary has to single handedly generate all the content, but they will combine the other members's contributions into a coherrent document. The secretary should also make sure that members are keeping their individual logs up to date. Your group meetings should be minuted by the secretary. This can be very useful if you can't remember what was decided!