Taking the time to over prepare and to practice can help in a way of shortening the time that you had originally thought you were going to be speaking. 

Placing yurself in an area where inattentive students are shifts their focus to you and the material that you are teaching. 

Policies and expectations as well as assignment reminders are helpful to students and you as an instructor. 

Have students work right away and have lectures last betweem 10-15 min. 

Get to know the students name and an ungraded pretest to see where they are at in the preogress of their development. 

Taking the time to migle and get to know the students before class would distract from wondering "how I will do?"

To captivate and motivate, one needs to be prepared and willing to connect and to exude excitment about their field.