How to drive your student crazy in 45 minutes?

Before going to the class where your students are waiting, you can finish your coffe quietly, or even go shopping if you wish. Anyway, you deserve to be expected! Finally, appear in the hall 20 minutes after the ring. 
Watch the phone as many times as necessary while your students are doing some boring exercises that you ordered. If a student asks if you corrected the last exams, answer that you didn't have enough time in these tree weeks.
You also can ask something to the more clueless or asleep student you see and stare at him even if he doesn't know the answer. Keep looking directly into his eyes and see the desesperation.
Order the longest work your creativity can imagine.  Obviusly it has to be delivered two days after because your students have nothing better to do! Everybody knows that youe subject is the most important one of all. And no doubt, don't permit group work.
Although the ring, continue with your explanation. You could continue next day, but you prefer to waste the 10 minutes of free time that students have.
Finally, say that you'll not be a few days in class, just before of "You're going to have a substitute". Yeah, it's the best thing you could say.