You're all wasting your money!!! You can get quality baseball instruction by going to you tube and typing in Domingo Ayala! He is by far the best baseball instructor in the country!
Seriously, if you want great hitting instruction just go out to Craig Ranch and sit in between the four-plex. You will hear great instruction coming from the stands all day.
Kidding aside, Curt Sanders is one of the best. He coaches one of the Dallas D-Backs 18U teams.