Summarize this article in one sentence.
In order to properly practicing blocking, you'll need three players. One person will do the passing, the second will try to receive the ball, and the third will execute the block. If you're practicing for the sake of playing competitively, it's a good idea to practice with your teammates. After all, improving their blocking skills will work out for your team just as much as honing your own. You should alternate between each of the three positions while you practice. This will make you a more dynamic player, and it will give the other players a chance to practice blocking too.  If you have a coach, he will try passing the ball. You can do this with two players as well. If you're blocking, stand in front of a wall and try to block shots from hitting the wall. A two player practice isn't as recommended however, as it robs the dynamic element from the exercise. The most common method of getting a foul call is through physical contact with a member of the opposing team. This happens often when players are attempting to block shots. As a result, you should cater your blocking to minimize risks of bumping into a player. This can be helped by jumping upward, and using your body as an obstacle, rather than actively reaching out and grabbing the ball. You shouldn't try to actively grab the ball out of the opposing player's hands. If you do, you'll get a foul call. A foul call will offer the other side a chance to get a 3 point shot without risk of being tampered with by your side. Although height and size are obviously important to shot blocking, agility is necessary in order to get you to a place where you can block. In competitive environments, opposing players are going to be moving fast. In most cases, you'll only have a few seconds to get between the other player and the net. Run to block the other player's path, and rotate quickly to face them. It may help to do "run and rotate" exercises in your own time. Luckily, these can be accomplished without help from anyone else. Keeping your feet in control during all stages of a blocking technique will limit the risk of a foul, and ensure you're in proper position to continue playing smoothly once the block is completed. Don't put one foot in front of the other. Keep them evenly spaced apart, and relatively parallel with one another. As you ready yourself for a blocking move, it's good to arch your legs in a squatting stance. This will give you the built-up force necessary to execute a proper block. Because jump shots are some of the most-used shots in basketball, knowing how to time your jump is imperative. Hold your blocking hand up to give yourself extra height, and jump up to meet the opposing player at his highest point. One way to time properly is to watch the other player's feet as they leave the ground. This will only allot you a split-second of time to react, but with enough practice, you'll begin to find yourself jumping on instinct. Jump directly upwards when you're blocking. This will limit the risk of coming into contact with the other player. In executing a block, you'll need to raise one of your hands up in the air to impede the ball's course. The surest way of deflecting a ball is to use the hand that's closest to the ball relative to your body. While most players will harbour a preference of one blocking hand over another, it's important to get both hands versed in blocking mechanics. This will make you a more versatile, and therefore more effective player. It's important to use your hand as an obstacle impeding the natural arc of the ball, rather than reaching out and grabbing it. Grabbing the ball directly could result in a foul call. Like all competitive sports, some of your success in basketball will rely on your honed instincts. This sort of thing only comes with a lot of practice. Even when you're blocking shots consistently, it's a good idea to keep pushing yourself until you're able to do so without consciously thinking about it.

Summary:
Assemble a group of three. Avoid contact with the shooting player. Run and rotate between the shooter and net. Stabilize your feet. Master your jump timing. Block using the hand closest to the ball. Practice until it's second nature.