Make sure you follow through on your swing,finishing high and down your target line. Check your grip and make sure you haven't gotten too strong and don't take the club back with your hands..If you take it away too far inside and don't finish correctly you will duck hook..Hope this helps..Good luck.

Well without seeing your golf swing, this is going to be very difficult to speculate on what the issue could be. There are a number of swing dynamics that could affect this type of solution.

Honestly I would find a local professional that does clinics and/or one-on-one instruction and tell him/her this is something you would really like to work on.

From personal experience what causes duck hooking is taking it too far to the inside on the backswing and overswinging.  The back foot gets stuck and you flip your hands over to release the club.  It is one of the two "over the top" motions.

I experienced the same issue at the end of this year.

1 week before my club's biggest event of the year member-guest tournament, one of my weekend playing partners mentioned to me that my club face was closed at address and at impact.

I thought this was odd because I am very pragmatic with my setup.

I then realized my left hand grip had slowly changed during the summer. I was holding the club in the finger joints of the 4th and 5th digits of my left hand.

by doing this, any amount of increased left hand grip pressure with the 4th and 5th finger resulted in closing the club face.

Try putting the butt of the club in fingers of your left hand including your 4th and 5th fingers, then grip the club normally with your right hand. Then address the golf ball normally.

Now simply squeeze the butt of the club with you left hand's 4th and 5th fingers while addressing the ball. You should see the toe of the club face close.

Now,regrip the club with the club butt in the palm of the left hand and repeat addressing the golf ball and squeezing the club with your left hand 4th and 5th fingers. The club face should remain square to the ball and target line.

Now hit a few balls with the adjusted left hand grip while applying medium left hand grip pressure. 

This worked for me with immediate results. 

My guest and I won 2nd place in the member guest for our flight. I shot my career best 76 on Sunday's final round.

I hope this helps. 

Brian

Tim...you appear to be left handed in your profile pic.

i am right handed, so please make note of this in my previous post.

Brian

Duck hooks, hate em', hate em' I tell ya.  Second shot from the ladies tee is embarrassing.  Those sneak into my game and are a wake up call for me.  My pro helped me with this problem.   To him, all problems start with the grip and he told me that as I play I am gradually rotating the right hand into a stronger and stronger grip.  And, he was right, now if I hit one I'll pay closer attention to the grip and it will fix the problem.  A tip I watched somewhere for adding a few yards to your drive, said to rotate the right foot out a little, gave it a try and it did add some distance, made my tee shots a little more accurate, but it has also virtually eliminated my duck hooks.  Those two things helped me but you may have something else at work, as suggested by others a pro might needed.  Good luck ...

Make sure you keep a smooth tempo throughout your swing and don't try and kill the ball.  That was my problem when i developed a duck hook. 

I had same problem. Golf pro saw me hit 7 driver shots and told me to shift my left hand grip so that my left thumb is almost on the side of the club. I am a righty. Felt weird but straightened it out.