I started using a hall pass to prevent my students from wasting time. They're only allowed two passes every nine weeks and if they want to leave the room; they are required to use one of these passes. This also teaches responsibility because they must have the actual pass I handed out to be excused from the room. There's no bookkeeping on my part. The students who choose to stay in class receive five extra credit points per pass not used. They must have the actual pass to get the extra credit though.