Learn how to release muscle adhesions, or knots, in your calves with a foam roller. Your calves are probably tight if your feet pronate (collapse in), or if your feet are externally rotated (turn out). Using a foam roller on tight muscles can help prevent injuries.
Learn to stretch your iliotibial band (IT band). Your IT band is probably tight if you feel pain on the outside of your hip or knee, or if your knees are adducted (cave in). Stretching a tight IT band can help prevent injury and reduce hip & knee pain.