Take a few minutes to analyze the video of your swing. Stop the video at several points during the swing (load, swing initiation, contact/impact, extension, and follow through) and compare to the pictures and descriptions below. How do you compare? Keep in mind that you can have several minor flaws in your swing, but if you keep your eye on the ball, get the barrel on the ball, and keep your bat speed through the swing, you can be a very good hitter. Also, every hitter has their own stance and style, but ultimately the stages of the swing below are very common among all good hitters.
Notice how there is more weight on the back foot and the upper body appears to be coiling or turning in back toward the catcher. Are you shifting your weight back and coiling your body as the pitcher is separating his hands? Are you keeping your weight centered on the inside of your back foot? Are your eyes focused on the pitcher's release zone? A common error at this point in the swing is only being 50/50 with the weight distribution as you begin to load your swing. Also another error is when the upper body does not coil and turn into the plate. Coiling the upper body creates more power as it uncoils during the initial forward motion of the swing.
Notice how each hitter has landed in a perfectly balanced position as their foot lands. Their hands push back to a fully loaded position ready to explode as the lower body begins shifting forward to foot plant. Are you getting separation with your hands during your foot plant? Are your hands at the height of your back shoulder and with barrel up and cocked back towards your head/helmet? Common mistakes during this phase is a flat barrel (almost parallel with the shoulders) and feet too close together.
Notice how the arms stay tight to the body and the belly starts turning out towards the pitcher. Does your elbow stay connected with the body allowing the knob of the bat to point at the pitcher and lead the bat through the plane? Does the bat stay close to the upper arm as the bat flattens out? Do the eyes stay focused on the contact point while your hips are turning? Common mistakes are the hands and barrel of the bat get away from the body (referred to as "casting the hands") and head turns with the hips, or the barrel drops below the hands (referred to as "dumping the barrel").
Compare the posture of your body at contact. Does your body (feet, legs, hips, and head) make the shape of the letter "A"? Is your head, shoulder, hips stacked (in a vertical line) on top of your back knee? Are you bracing on the front side or do your hips float forward? Is there an "L" shape made with your back leg? Are your hands palm up and palm down at contact squaring up the ball? Are your eyes focused on the contact point? Common mistake is reaching for the ball and trying to strike too early with the result of pulling most all of your hits (or missing entirely). Let the ball get deeper so that your arms are not yet extended as you make contact.
Notice how the hitters extend to a "Power V" position with their arms. They continue to brace on the front side (leg and hips) as their top hand starts to rotate over the top of the bat. Do both of your hands stay on the bat and arms extend to the shape of a "V" after contact? Is your stomach and hips totally rotated towards the pitcher? Does your head stay down and over the top of your hips and back knee? Common mistake is rolling the wrists and wrapping the bat around the body thereby striking the outside of the ball, versus pushing through the zone with the bat after contact.
Notice how the hands stay high on the follow through. Whether one hand or two hands on the bat, the hitter finishes the rotation whereas the back of the uniform rotates entirely to the plate. Are you finishing your swing and rewrapping the bat around your body? Does your front arm fully extend whether one hand or two hands remain on the bat? Common mistakes include letting go of the top hand before fully extending resulting in a bent arm held around the belly/waist. Also, dropping the hands as the bat and hands slow immediately after contact.