The distance a hitter stands from the plate depends on his body structure and style of hitting. Basically, a hitter should stand far enough back from the plate so that his bat passes slightly across the outer edge of the plate when his arms are extended. This position encourages a hitter to "throw" the bat at the ball and to extend fully on all pitches.
Standing too close to the plate makes it difficult for the hitter to execute a proper contact point position, and may lead him to swinging with his arms instead of throwing the bat at the ball.
The hitter's belt buckle should be in line with the center of the plate and the stance should be slightly closed (the front foot slightly closer to the plate than the back foot), with the stride going toward the pitcher's belt buckle. This position enables a hitter to hit all types of pitches more effectively. The hitter will be able to contact the curve ball before it reaches the maximum breaking angle, yet the position still permits the hitter to pull inside fastballs.
Excerpt from Ch. 1, pgs. 18-19