Why is a stance so important?  It's all about gaining quickness with balance on the first step! A lesser sized player with proper technique can win the first step battle and beat his opponent in the trenches.  Also, with a balanced stance, the opponent will not be able to predict where that first step will be.  While size is very helpful, quickness and technique will win. 

(1) Tail Down = Eyes Up
With the tail lower than the shoulders, the head and eyes are upright and able to see the field.

(2) Inside Hand Down and Forms a Tent.
Inside hand is down.  This means the hand closest to the football is down. Forget about thinking this is too hard to teach.  It is easy.  It is not like throwing a ball, or shooting a basketball.  We are talking about a stance. Easy to learn when practiced. Players need to learn both a left handed and right handed stance.  This is important!  The down hand should be inside and closest to the football.  This is a major advantage in protecting the inside gap.

The hand should have very little weight.  The hand should be able to lift off the ground for a second without the player falling forward. The hand placement should be forward; at least under the chin.

(3) Front Foot is Flat on the Ground.
The heel should be flat on the ground without any air.

(4) Forearm "Presses Down on the Knee/Thigh.
The hand should be relaxed.  The upper body weight should be resting on the thigh. The players weight should be mostly on the front foot, with the upper body weight resting on the formarm.

(5) Make sure there is a "Slight" Heel-Toe Stagger.
The toe of the foot behind the down hand should be behind the heel of the foot under the forearm relaxed.  For Guards and lineman that pull, this stagger mey be a little less, but needs to still exist. The toe of the back foot, need to be lined up behind the heel of the nearest player to his inside.

(6) Feet are shoulder width apart.
If the feet are too wide apart, there is no power or quickness in the first step.
Remember, Toes are straight ahead. The knee on the upper foot should be facing the opponent.

(7) Keep the Weight Back.
With the weight back, the head is up. tall, and eyes facing forward.

(8) Keep Down Hand Lined Up with the Back Foot
With the hand and foot in line, the players stance is properly balanced. With the proper stagger, and having the inside hand down, then the down hand lined up with the back foot, the players hips are naturally turned open to the inside.  Together, these provide a natural advantage for a player to cover or attack the inside gap.