The putting grip should be in the lifeline of your left hand instead of in your fingers and underneath your heel pad like in the regular swing
What really differentiates players is their short game, and juniors should take a tip from the pros and spend at least half their practice time on the short game
Advanced player looking to add more width on their backswing and improve their left arm position should try this neat little drill from Vijay and put a headcover under their right arm