Lefties only golf tip: A key way to actually get your arm as nice and loose and nice and relaxed in the golf swing is to make sure they are hanging correctly at address. When are getting into a posture or position where you want to be swing is your arms hanging down from your shoulders pretty much pointing straight at the ground.
Left Handed Golf Tip: Correct Arm Hang And Posture To Keep Relaxed During The Golf Swing (Video)