Keep your core engaged (think about holding your rib cage down as you "zipper" your hips up towards your belly button), then step one foot forward and rest just on the ball of the foot. Close your eyes. Try to ground through your foot, making a foundation from your big toe, through the ball of your foot and back through the heel, trying to keep your arch from collapsing. Try to hold until you feel you have gained your balance. You can start to challenge yourself by lifting your foot off the floor a little more as you start to build your proprioception, getting all the way up to A march position.