Most people roll up their yoga mats after class, but that transfers germs from the underside (floor) to the top side that you stand and lie on--ew! Use this trick to properly fold your yoga mat and keep the top side away from the germy underside.
Before rolling up your mat, simply fold it in half. That keeps the top side you use touching itself and the bottom/dirty side away from it. Then roll up your mat. Simple and easy! Of course, you should always wipe down your mat before and after each use, too. :-)