Basketball Defense Fundamental #1) Basic Stance
Keep your feet positioned as wide as your shoulders with your weight balanced on the balls of your feet. If you're flat-footed, back on your heels or have your legs too close together, it's hard to move quickly and you'll find offensive players dribbling right around you. Keep your knees bent slightly with your butt low. Now, make sure you have one extended high to guard shots and passes and the other hand extended low on the ball.
Basketball Defense Fundamental #2) Focus On the Waist
If you want to avoid getting faked out, focus on a part of the offensive player's body that doesn't move. Many inexperienced players focus on the eyes, head and legs of their opponents. Or, they watch the ball. If you watch the ball, all the offender needs to do is fake a pass, fake a shot, or fake going one way and go the other way. Don't do this or you'll be sucking air as the offensive player goes in for the lay-up! Remember to watch your opponent's mid-section because they can't go anywhere without it. If they fake a pass or shot and then do something else, you'll be right there because you'll see the waist go where they really intend to go.
Basketball Defense Fundamental #3) Slide Side-to-Side
Position and footwork are two of the most important aspects of playing good basketball defense. Be sure to move side-to-side (laterally), without crossing your legs. As you slide, maintain your balance by keeping your feet as close to the width of your shoulders as possible. Also, avoid letting your feet to touch as you move.
Basketball Defense Fundamental #4) Be Aware of Tendencies
Becoming a good student of your opponent will turn you from an "OK" defensive player into a great one. You want to find out whether they are right-handed or left-handed. Do they like to drive to the hoop or do they prefer making jump shots? The key is to get your opponent doing the opposite of what they like. If they like making jumpers, try to make them drive. If they like to go to the left, make them go to the right.
An important element of this strategy is good footwork. If you're trying to make an offender dribble to the left, keep your left foot slightly in front by dropping your right foot back. Stay on the balls of your feet. If they still try to go right, you're in position to move in front of them. If you're successful in making them go left (your right), you can move quickly that way. Reverse this basketball defense strategy to make them go right, of course.
Basketball Defense Fundamental #5) Guarding the Offender
There are two important fundamentals to guarding players without the ball: Stay between the player and the basket and try not to turn your back to the ball. If the player you're guarding is on the right side of the floor and ball is on the left, raise your left hand and drop your right foot back a bit. Be sure your left arm is between your offender and the ball but don't turn completely around or else your back will be to the ball. Keep your head up so you can see your opponent and the ball at all times.