Lefties only golf tip: Once you have identified what the issue is, how you are swinging from out to in, if it is the that you have on your side, if you are not transferring your weight or if your hands are moving out and away from the body, a key area of the swing to really focus on is the transition between the top of the back swing and the start of the down swing.
Left Handed Golf Tips: Stop Rushing From The Top Of The Golf Swing (Video)