Coaching 101 has a great article about "the art of getting open" while playing "Territorial Sports."
Winning the foot war is the first skill listed.
In basketball, there are two ways to win the foot war:
The first, and most popular one, is in the post. Post players always want to have their foot ahead of their opponents' foot. If they are on offense they want to work to get their feet ahead so they can effectively post up. If they are on defense in the low post they want to put one foot ahead of their opponent so that they can position themselves between their player and the ball. A great example of this is included in the book Playing Big by Pete Newell, on pages 50-52.
Newell writes, "The defender avoids lower-body contact for two reasons: to keep the legs free to get into the passing lane, discouraging a direct pass into the post; and, if the ball does go in, to keep the legs free to stay between the ball and the basket. When both players work to achieve their goals, a 'foot war' results." View the pictures on this link.
Players should work on winning the foot battle by practicing with a teammate to establish position in front.
The second way to win the foot war is through guard play. Many people have heard the saying "speed wins" and although this is often true, one does not have to be fast to be quick. Guards who can establish getting their first step past their defender's lead foot will win the foot battle.
This video from CP3 The Teacher teaches how to attack the lead foot.