Gather your students outside the classroom -- say, outdoors at a picnic table or on a few blankets on a grassy hill. Explain that just as they took steps outside the classroom, they're also about to go outside their normal daily routine by embarking on a project in which every student will participate.
Explain that a project, by definition, requires an in-depth investigation of a real-world topic that should complement a lesson in the classroom. Ask students for their ideas and then vet them for relevance and age-appropriateness. Depending on the number and veracity of the ideas, decide whether the class should work on one project or broken down into groups to work on several projects at once.
Create a "job board" that explains the project approach so it resonates with students. Assign each student a task; be as specific as possible. For example, if your classroom project is starting a business, assign one student to research the competition and others to be responsible for accounting, marketing, day-to-day administration and other duties.
Give each student a specific deadline for each task, encouraging them to collaborate with others for the fledgling business to succeed. Spell out consequences if deadlines aren't met.
Develop a "team resource center" where students feel comfortable collecting information, discussing ideas, debating disagreements, forging agreements and working as a team.
Remind students periodically that all good projects -- like all good stories -- have a beginning, a middle and an end. By extension, if students fall behind in their tasks in the middle of the project, they'll have to put in extra time to ensure the project is completed on time.
Schedule a meaningful culminating event in which the group presents its project and each student explains their role in it. Give students the freedom to present a written report, give a verbal presentation or role-play. The project approach is inherently designed to play to students' natural strengths so they learn as much as possible from a project and life skills along the way.