TIPS:

Bat Angle
Correcting a Weak Swing
Finishing the Swing
Flat-Snap Hitting
Front Toe Closed
Hitting Off Front Leg
Level Swing
Looping
Lunging and Over Striding
On-Deck Preparation
One Swing
Perfecting the Stride
Plate Coverage
Poor Timing
Proper Hitting Goals
Seeing the Ball
Stance vs Swing
Staying Closed
Stepping Out on Pitch
The Two-Strike Swing

Most of these tips come from the book Illustrated Hitting Guide with permission from the author.

On-Deck Preparation 

Many young players waste valuable time waiting for their turn to hit. They stand in the on-deck circle and talk to teammates or take lazy swings with the bat. Poor on-deck preparation reduces their probability for success. Good on-deck preparation should include the following:

  • Position yourself in the on-deck circle so that the pitcher and home plate are both in view.
  • Quickly loosen up your muscles by swinging the bat back and forth and over your head.
  • Take your stance and focus on the pitcher.
  • When the pitcher releases the ball, stride and then swing hard, the same way you plan to swing when getting up to the plate.
  • Time your swing so that your bat head crosses the plate before the ball does.
  • Make timing adjustments on the remaining pitches until it’s your turn.
  • When leading off an inning, don't waste time talking. Go time your swing.
  • Do not use a bat donut on-deck. This will throw off your timing. Studies have found that the probability of hitting the ball on the first swing is lower for players using a donut on-deck.