Coaches always tell their players to watch the ball all the way to the bat. But, where should you pick up the ball as it comes in? If you don't pick the ball up as soon as it leaves the pitcher's hand, then you reduce the time you have to react and may miss early indicators of the type of pitch being thrown.
There are a number of ways to pick the pitch up out of the pitcher's hand.
As a hitter, you can gain an advantage if you can correctly predict which pitch the pitcher plans on throwing. You can often determine what the pitch is by the way the ball comes out of the pitcher's hand.
For example, a fastball comes straight out of the pitcher's hand where a curveball pops out above the hand. To determine these pitches, stand behind a backstop and concentrate on the pitcher's release point. While this takes practice to perfect, you will become a more patient hitter who can better predict the pitches thrown your direction.
Arm position can also determine the pitch, especially a pitcher who has a three-quarter arm motion. For these pitchers, they need to get on top of their curveball and often throw pitches with their arm in a higher position than when they throw a fastball.
Let's go back to the imaginary box example. If you focus in on the box and you know the fastball comes from the middle of the box and the curve comes from the top of the box, you will recognize right away when a curveball is being thrown.