I believe that hitters can develop plate discipline, patience or pitch selection.  Some hitters seem to develop this more easily than others and some hitters seem to be blessed to start further along the curve than most.

This question is addressed to John and all others that are knowlegable on this topic:

What/How would you go about instructing a hitter to develop his plate discipline?

a) What swing mechanics are key here?  
I feel that good balance over the back leg is very important.  I also think being loaded by/at the moment the pitcher is about to release the ball is important.  I feel that these things allow the hitter to see the pitch longer, which gives him a better chance to decide if the pitch is a ball or strike, inside or outside, type, and speed of pitch.

b) What mental gameplans are we looking at?
I feel that knowing the external situation of the game: tendencies of the pitcher, pitches the pitcher is throwing for strikes today, score, runners on base, etc. is important because it will help a batter know what pitch will likely by thrown and its location.
I learned to anticipate every pitch being a perfect pitch to hit until I decided it was not, which really helped me be ready for every pitch.

c) What physical drills can be used to help develop plate discipline?
I feel that tracking pitches while guys throw bullpens helps a lot because it helps develop where and when to "see" the ball at its release point.
I feel that the "tennis ball machines" with colored numbers on them are very helpful to develop pitch recognition.

Thanks.

As a Cubs fan I have followed the Cubs since I was young.  I have never seen anyone mention the effect that Jeff Pentland may or may not have had on Sosa's development as a hitter.  It seems that his arrival precipated a change in Sosa's stance, load (the step back and then forward), and at-bat plan.  These changes seemed to spark the amazing run of offensive numbers he put up over several years.  When Pentland was let go it seemed that Sosa started his decline.  It appeared that the patience (not swinging at sliders in the dirt) and the gameplan slowly changed and I saw a Sosa swinging much more like he did at the beginning of his career.  I'm curious to see what anybody else noticed this.  How much of his success can be contributed to his batting coach, pentland?  I feel that he was a big part of Sosa's success.