Hold the clarinet properly. The left thumb should cover the thumb hole on the bottom of the clarinet with the tip ready to play the register key. The index, middle and ring finger of the left hand will cover the first three keys on top. The pinky of the left hand occupies the nearest extension key. The right hand uses the index, middle and ring finger on the next three keys. The right pinky plays the extension keys at the end.
Cover the thumb hole with the pad of your thumb and use the tip of the thumb to press down on the register key.
Use a firm embouchure in which the muscles of the cheeks and mouth are squeezed together. Blow a quick, narrow stream of air through the clarinet while covering the thumb hole and register key.