Check attendance by scanning the room while your students are working independently. Assign an appropriate amount of work. Fifty math problems may not be as effective as 15 done correctly. Finding the appropriate pace of a lesson is not an easy thing to do, but careful pacing will prevent frustration and wasted time. Have alternative assignments for those students who finish an assignment ahead of the others.
Many students waste precious time waiting for others to finish.
Make sure the topics you assign are relevant and necessary for your students' immediate and future needs. Your students should understand their importance. Plan your classes so that students are engaged from the minute they enter the room until you dismiss them. Resist the temptation to be distracted during a lesson by students who want to chat or otherwise stray from the topic. Establish and follow a routine set of procedures for daily classroom chores.