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.

Bat Angle

Use the correct bat angle for better hits!

The angle of the bat in the stance isn't very relevant as long as the bat is in the proper position in the launch position (or after the stride when the foot is planted and the hands are over the back foot). When the hitter has no indication of whether or not the pitcher is throwing consistently high or low, the bat angle when the swing is about to begin should be at a 45 degree angle. This maximizes the opportunity of being able to hit a high strike and a low strike solidly. When a hitter notices that a pitcher is keeping the ball down consistently, he can look for a low pitch and angle his bat up (point the knob toward his feet and the barrel toward the sky). If the pitcher is throwing high, the bat can be flattened a bit prior to the swing. Changing the angle will keep the bat head in the hitting zone longer when in fact it corresponds to the height of the pitch. Generally, looking for a high or low pitch should take place when there is some consistency on the part of the pitcher and when the hitter has less than two strikes. With two strikes, the hitter needs to be ready for all pitches in or near the strike zone.