All this talk recently about Stewart taking too many called third strikes got me to thinking: how do players become good at fowling off pitches with a two strike count?  A few days ago, Todd Helton worked a 14 pitch at bat before hitting a home run.  As Jeff and Jack were commenting on the radio, he is one of the best in the game at doing that, which is why he has been so successful in the big leagues.  Also, there was an article on ESPN.com recently discussing hitters' approach at the plate, whether it is aggressive (Franoeur) or selective (Pujols); the ultimate conclusion was that it varies from one guy to another. 

So how do guys learn to be patient and lay off the slider down and away, while still being aggressive on pitches in the zone?  And do hitters practice spoiling pitches, so that they can get one to hit?