A good yoga mat can help your balance and coordination. It should provide excellent support between you and the hard floor; any place you do not naturally have padding will love you for using a good mat.
A good yoga mat should last for years and help you with your exercises.
You want a lightweight, dense mat that you can wash. It needs to not be slippery when your feet are sweaty, you want it to remain on the floor, and you want small debris to be able to be brushed off of the mat.
When you examine a yoga mat, first check how dense it is by pinching it between your thumb and finger. The denser it is, the better. Then moisten your hand and test the "wet friction" of the mat. Lastly (and only do this with permission or on a mat sample), take a quarter ( the coin ) and grip it tightly in your hand. Rub it along the surface of the mat until you get the surface to break down; the more strokes it takes, the better. ( This tests how long the mat should last ).
Don't skimp on your mat; it's the most important pieces of equipment