Outlaw "I'm Done!" I LOVE this post from Kady at The Teacher Trap. She makes some really good points and includes suggestions for helping kids change their mindsets about rushing through their assignments.
Each student is given a ticket (from 1 to how ever many students you have in class) at the beginning of class and meets me at the designated conference area in the room when they hear the & and their number appears on the projector screen. Kids love it!