In the video below Michigan State Coach Tom Izzo breaks down the basic principles of a defensive stance.
Coach Izzo has his players square their feet to the offensive player. He does not have them put one foot up and one foot back. If he wants to force a player in one direction he has his defensive players move one step either to the right or left and split the stance of the offensive player while still squaring up to the offensive player.
Coach Izzo also states that he has his players put one hand up while in their stance and stresses the importance of not only contesting shots but contesting passes while in the defensive stance.
This clip was taken from a complete coaching course.
For more information about that video course click the following link: Tom Izzo Defensive and Rebounding Skills
The clip below has audio so please make sure you are not muted and the volume is turned up.