The content of this post may seem obvious to some of you, but to others that haven't tried using a timer before, I invite you to try it...I bet you will love it.
I often have my class work in groups...sometimes they are working on task cards, sometimes a review sheet, sometimes talking about a couple of problems. But group work sometimes ends up in a black hole - some groups finish and are really focused, some groups work well together naturally, but other groups end up talking about things other than the math assignment!
One thing that really helped me this year was using a timer to keep things moving along. You could use any timer, but the kind that really helped me was a digital timer that I could project onto the front board. (There are many available online for free, but here is the one I used: Online Stopwatch )
The advantages that I found while using a timer were:
1) A timer allowed me to keep track of how long the students were working.
2) A timer allowed me to hold students accountable for the task at hand.
3) A timer created a sense of urgency that the task needed to be completed and the students needed to keep working in order to get it done.
4) A timer allowed me to do something else - for example, take attendance, quickly grade a makeup quiz, etc - without losing track of the time.
5) Finally, a timer will not allow one group or student to monopolize your time...or a timer will allow you a specific amount of time to work with a struggling group or student.
I am definitely going to continue to work with a timer next year!