And best of all it is almost legitimate!
Things you will need to pull this off:
1 cell phone with digital reminders capability.
1 class that you know you don't want to sit through beforehand.
1 teacher that doesn't allow cell phones to go off in class
Step by Step instructions:
1) Before class starts, take the teacher aside.
2) tell him you need to leave your cell phone on so you can be alerted to some unpredictable event. (Today I used, "A friend of mine is having a baby today.")
3) Once the teacher agrees to let you leave your phone on, set up a reminder to go off about 20 minutes into class.
4) Pick up your phone and act like you are talking to somone(quietly, you don't wanna disturb class

)
5) Look over to the teacher and nod a few times.
6) Pack your things and leave
7) Enjoy your semi-legitimate freedom
--Xelah
*combining technology, imagination, and boredom to pioneer new ways to goof off*