Blocking is the quickest and the hardest way to get a point. More importantly, however, it is the easiest way to change the momentum in a match and/or demoralize your opponent. First of all, it is hard to block well if you don't jump well or if you aren't 6'0". It is important that you can reach about 9'0" or 9'6" feet in the women's game. If you can't reach that high, you will still be able to do the things that are discussed below, just with a lot more effort and accuracy. Most attacks cross the net at the 8'6" level or lower even when they are attacked at a higher level. Here we go...
We won't discuss where to line up according to the sidelines or middle blockers since this will surely vary according to the opponents offensive scheme and other variables. Instead, this paper will speak in general terms and some modifications to this protocol would be necessary in specific situations. As soon as the ball is set and you realize that the ball is coming to an attacker that you are responsible for, your first step should be to the area that you are to cover (cross court or line.) In order to move to the correct area to block, take your eyes completely off of the ball (this is very difficult to get yourself to do) and watch the attacker's approach. This will help you to line up perfectly with the attacker. Again, where you are lining up according to the attacker (off her hitting shoulder, lining up her attack shoulder with your outside shoulder, your right eye with her left nostril) will all depend on the defensive scheme you are executing at that time.
Setting a good block communicates to the middle blocker where she has to "close" to. If you are going to move at the last second to your "area" the middle blocker will either crash into you or leave a huge "seam" in the block (more likely) and your block will be very unstable leaving your defense for target practice. Now, let's talk about the "area" we are covering. Again, this will vary with your team's defensive scheme that was designed to effectively defend your opponent's attack. Nevertheless, your area should be covered by the area your body would cover if you jumped straight up (which, in optimal situations, would be the best procedure)--in other words, line up on the floor in the area that you are responsible for taking away from the attacker. However, optimal situations usually happen to us once in an entire tournament if we're lucky. And here is where blocking strategy starts to stray from the norm--when we are airborne, we can do many things...
There is nothing easier to hit around, over, and off of than a motionless block. As you remember, you had taken your eyes off of the ball in order to watch the attacker's approach. When should you leave the ground after you've set the block? The only rule that is universal is to leave the ground after the hitter does. How long after will depend on your vertical and theirs. Experiment with jumping at extremes--really late, or a lot earlier than you usually do and find what works for you against different types of players.
Now we are airborne. Remember that your first priority in blocking is to take away your area or make the attacker really believe that you had your area covered (hence, leaving the ground from the spot along the net that would allow you to cover that area) and then adjusting the penetration of your hands, angle of your hands, angle of your fingers, and angle of your arms to fit the attack. Sometimes this meant to simply jump and reach straight up and stuff the ball. Sometimes this meant to jump and, at the last split-second, reach horizontally along the net and stuff a cross-court shot, or a seam shot, or any attack meant to go beside your block. Sometimes this meant to drop your arms at a backward angle with the palms facing upward to soft block someone who just out-jumped you by 2 feet or someone that hits off the top or over the top of your block every time.
Let's go through the thought processes after you are airborne. After you've seen the approach of the attacker, you'll probably know which shots she is most likely to make, or the shot that will be her "best" or most powerful one. The way her hips are facing when she leaves the ground will be the easiest way for her to get the maximum power for the attack. Your hands should start reaching and penetrating in this area first as you ascend. Now comes the tricky part. This is where we get to use our peripheral vision. It is now pertinent that you watch the ball while you are watching the attacker's shoulder girdle (upper body)--kind of like how you watch the block as you attack the ball. This is important because if the ball is tight, your course of action as the blocker will be different than if the ball is farther off the net. The angle that the ball is being attacked from is important as well--for example, if the ball was set to the left side from 20 feet off the net in the middle of the court, the attacker's hardest shot would be a line shot. If the ball was set from the net to the left side and 10 feet off, any extreme shot will be very difficult.
Now that you know where the ball is and where the attacker's easiest attacks are, your blocking stature will react in the most effective and efficient way in order to prevent the attack from crossing the net, slow the ball down, or direct the ball to your defense--these objectives are listed in order of priority. If we can stop the ball from even coming to our side of the net, then that is simply at the top of the list of priorities and so on.
As you reach the peak of your jump, your last adjustments are made. If the ball is tight enough for you to reach (and low enough), reach with "strong" hands around the ball--your outside hand beside and on the top of the ball (so that the attacker can't wipe the ball off you and out of bounds) and your inside hand behind and on top of the ball. Oh yeah, don't touch the ball before the attacker does. Sometimes the ref will get mad.
If the attacker is turning her hips and/or shoulders down the line, cross-court or generally away from your block, now it's time to reach. The important lesson here is to know when to reach--know your capabilities, realize whether or not you got a very balanced jump (you don't want to reach your way into a net violation), recognize if you are above or below the ball and net (this will help you decide whether or not to soft block with your hands facing upward or to attempt a stuff block with your palms facing downward--being above or below the net will dictate where your arms and hands are positioned--off and below the net or penetrating above the net, etc..
Now it's time to talk about the disadvantages to this technique. This technique can work against you if you don't develop it correctly. Judgement is a big part of this technique--knowing when, how much, and where to reach; knowing the correct angles to place your hands and arms; simply learning how not to get used.
Here's some quick tips on blocking--
Like every other part of this game, blocking is extremely hypocritical. In other words, you assume that the attacker has no control over the situation, but that you, the blocker, have complete control over the situation. While, at the same time, when you are attacking, you feel that you are in total control. This is so essential to this game in part and in whole. You must always believe that you have total control over anything that happens on the court at all times--no excuses.
Give credit where credit is due, but not during the game. If the ball gets past your block, it's your fault. Touch that ball! While following the protocol discussed earlier, have a hunger and determination for getting your hands on the ball in a strategic way. Keep strong hands and shoulders. There's nothing worse than being lined up perfectly for a block and the ball getting hammered through your hands or arms. Shrug those shoulders and extend those fingers while flexing every muscle in your body (including your abdominal muscles). Keep your eyes open. Watch the ball and the attacker according to the protocol discussed earlier. Getting hit in the face doesn't hurt that much anyway.
When in doubt, be static. If you're off balance, out of position, or simply out of control, it's better to set a block that doesn't end in a net violation or an unreadable floating, flailing block that ends in an unexpected attack angle that couldn't be dug by 50 defenders on the floor behind you (note: only six players per team). Penetrate! If you penetrate, you take away a lot of attack angles from the opponent. If you don't penetrate, well.. you're easy. If you're short, use your arms to help you jump. Practice using your arms effectively without bringing the bottom of the net with you on the way up. Keep your hands apart. There are a lot of coaches that would disagree with this, but keeping your arms less that a ball with apart is ineffective. Sometimes your hands are a lot less than a ball width apart, and sometimes they are 3 feet apart--the better to cover many attack angles.