Summarize this article in one sentence.
Point your feet forwards and place them just wider than your knees, which should be comfortably shoulder-width apart. This stance will already start to lower your center of gravity and give you a strong base. Shift your weight into the balls of your feet and lift your heels just slightly off the ground. Bend your knees and lower your body into a strong squat position. A good rule of thumb is that if you think you’re low enough, try to get lower.  Focus on keeping your weight in the balls of your feet, but not in your toes, which will throw you off balance. To test how low your stance is, reach down with one hand. You should be able to touch the ground with your fingers. You should still be able to move easily; if you can’t, ease up on your squat just a bit. Keeping your weight low and centered on the balls of your feet will help you stop quickly, accelerate faster, and react better to the ball. Your back should be level from your shoulders to your hips and slightly arched, but not totally straight. To help you get a feel for the posture, reach your hands down to the ground while sticking your chest up. Your upper body will lean forward a bit, but keep your weight balanced.  This stance might seem uncomfortable at first, but it will feel more natural with practice. Making sure your back is flat will protect it from injury while keeping you balanced. Experiment with placing your hands out to the sides, or placing one hand wide while keeping the other at the offensive player’s hip or using it to dig for the ball. Whatever you do, don’t let your hands fall to your sides. Your coach might have a specific hand placement they want you to use depending on how aggressive your defense is. If not, just focus on keeping your hands up and active. Try different positions and see what feels natural and effective.

Summary:
Set your feet slightly wider than shoulder-width apart. Put your weight in the balls of your feet and bend your knees. Keep your back flat, but not totally straight. Raise your hands and keep them loose and active.