Go for a walk after class

And leave your ipod, cell, and laptop at home.  You'll learn more:

Your Brain on Computers - Digital Devices Deprive Brain of Needed Downtime - NYTimes.com

“Almost certainly, downtime lets the brain go over experiences it’s had, solidify them and turn them into permanent long-term memories,” said Loren Frank, assistant professor in the department of physiology at the university, where he specializes in learning and memory. He said he believed that when the brain was constantly stimulated, “you prevent this learning process.”