One of the most asked questions that I get as a Teaching Professional is “How am I going to fix my slice!?” There are a few fundamental things to look for that can cause this shot:
Check your left hand grip – are you seeing 2 ½ or even 3 knuckles, not one or two?
Ensure your shoulders are square to the intended line, not aiming left of the target if you are a right handed golfer?
Is the club going outside of the intended line on the backswing? Check the direction of your backswing and ensure it starts back on a semi-circle direction moving slightly around behind your body rather than outside the line.
Are you rotating your shoulders enough (if you are a right handed golfer, your left shoulder should turn until it gets under your chin).
Your downswing should follow the same direction as your backswing.
A simple drill to help make this work is the “right foot behind left foot” drill. Swing the club back and through, keeping your right foot on the ground the whole time. This drill helps with the direction of your swing and helps correct your hand action as you hit the ball.