To improve your hitting, you need to train in environments that prepare you for what you'll face in real games. One way to do this is to use a two-machine system with fastball and curveball timing chutes to simulate pitch delivery.
With this system, you can use Marv balls (foam baseballs that won't sting on a missed hit and require more accuracy with the barrel). Both balls travel down the ramp at the same time, and the hitter listens for a verbal command (1 for fastball, 2 for curveball) and must hit the correct pitch.
This simulates a real game situation where the pitcher is attacking the hitter with two different pitches. The hitter must have adjustable timing, take when needed, and swing when needed. You can also add counts to the drill to work on approach and situational hitting.
Stay focused. Listen carefully for the verbal command and focus on hitting the correct pitch.
Have adjustable timing. Be prepared to adjust your timing for different pitches and speeds.
Take when needed. Don't be afraid to take a pitch if it's not in the strike zone.
Swing when needed. When you get a pitch in your zone, be confident and aggressive in your swing.