How do we ensure accountability when students are working in groups?

A major concern is each student doing his or her own work.
Each student must be monitored and complete/submit daily tasks
How do I know if each student is contributing?
1.Each student uses a different colored pencil to do problems and answer questions.
2. Students get TWO grades for group is for the actual project/assignment; the second is a individual work grade [up to 10 points according to how much the group thinks he/she worked daily]

There's only one of do I keep each group focused while monitoring other groups?
Delegation! Assign each student a "job"...the noise monitor ensures each member is working quietly and focused. If a problem arises, this student tells the leader who attempts to re-focus the student not working. *if it's necessary, the teacher steps in after the leader has a conference with teacher*
One major concern is to keep each student engaged and on task while he or she is helping to complete the group assignment on time.
Students can be given roles within the group. (There can be recorders, researchers, time keepers, or any other job description that may be needed to accommodate the types of groups needed for a given class.)