Nothing in badminton is more important tan starting with the correct grip.
Proper grip is the foundation of good badminton play.
Improper grip restricts arm movement causing muscle fatigue and decreased stroke effectiveness. Check to see if there is a V on the top formed by the thumb and index finger. Check the end of the racket to be sure the butt of the racket presses into the heel of the hand. This allows the thumb to push the racket through the air and provides greater force and speed. This grip is assumed by laying the racket on the floor and picking it up with the V on the upward side.