You've literally spent years of your life studying. Studying more efficiently, even by a little bit, could add up to a huge store of additional knowledge over a lifetime. Efficiency can matter a lot. So of course you got extensive training on how to study effectively, right? Probably not. I know I didn't.
A New York Times article explains that students, teachers, and parents often believe in study techniques that are basically old wive's tales.
But that doesn't mean there aren't effective study techniques out there. As the article says, "In recent years, cognitive scientists have shown that a few simple techniques can reliably improve what matters most: how much a student learns from studying."
It's really fascinating.
http://www.nytimes.com/2010/09/07/health/views/07mind.html?src=me&ref=health