Service learning can occur through an individual assignment or a group project. In my communications class, I choose a project-based style because (1) it encourages group communication, (2) it creates stronger interpersonal relationships, and (3) students learn about project management. Not every class is right for group projects, but if your goal is to build leadership skills and communications skills, then I suggest forming groups in the beginning of class and giving them as head's up that they will have to work together on a community service project.
The other day, I walked into the college's lobby area where students meet and talk. Right in the middle of the lobby, one of my service learning groups were sitting in a circle. Their body language seemed warm and personal. They were discussing their projects but laughing and listening to each other. That's exactly what I wanted to see! Would this have happened without the service learning project? Perhaps, but I feel it creates a special bond between peers as they work toward a common goal: to serve the community. Grading this type of project is somewhat challenging, but if you work on a matrix of what you want this group to achieve, then the process can become quite simple. And there is a bonus! You're helping your community.