Three Classic Swing Mistakes

Blocking the Front Arm - The player locks or stiffens the leading arm as the swing action starts. Lots of young players will have assumed the correct stance and release positions but tend to tighten up as the swing starts.
 The barring of the front arm will cause the swing to loop and be too long. The batter has trouble taking the bat to the ball and making contact unless of course the baseball is thrown exactly on the swing plane.
The correct swing action features a "quick stroke" or path to the ball.
The easiest way to fix barring the front arm is to make sure that the player maintains leading arm elbow at an "L" position prior and during the swing.

Stepping out or Pulling Off Pitches - My coaches and I often observe this with children in our summer camp program. They always step out and their front side often flies open before the ball arrival.
This particular player has serious trouble generating contact.
Before this flaw is actually remedied, the player is only going to become discouraged and self-conscious.
To maintain leading shoulder within the correct "closed" position, train the player to hold the front shoulder closed and aimed at the 2nd baseman for right-handed players and toward the shortstop for left-handed players.
 The stepping out is really a harder flaw to correct.
Getting the player to pick the front heel up and stepping just a bit towards home plate can help. My coaches and I do not encourage placing obstacles behind the front foot to help keep it from shifting backwards, even though a lot of coaches try this to prevent this kind of poor habit.
We frequently utilize the "step in and hit: exercise using a batting tee.
The player assumes a posture off from the baseball target that needs the player to step towards the ball to be able to help to make contact.
If your player doesn't step towards or to the baseball, the player may struggle to hit the baseball.

Upper Cut Swing - The upper cut swing might be due to a couple of things which are easily determined.
Dropping the hands and back leg collapse may both result in the player swinging upward.
Be sure that the player retains his hands at the top of the strike zone and doesn't move the hands or drop the back side shoulder during the swing.
The rear leg ought to be kept straight to avoid back side dipping which could likewise trigger an upper-cut swing.
An excellent drill that we utilize to prevent this is the soft-toss drill.