The less tense you are, the more fluid your swing will be. Where does tension show up in your swing? Does it show up in your arms, hands, shoulders or jaw? Figure out where you have tension in your swing, then work on relaxing that area.
One Drill from instructors Pia Nilsson & Lynn Marriott is the potato chip drill. Put a tee between your front teeth and hit some shots. Hit any club and feel the light pressure holding the tee. Another way to do this is to put a potato chip between your front teeth. Hit any club you like without biting the chip in half.
Give it a try.