If you're slicing and you think you're doing something wrong, don't worry. You're not. It's natural to slice. Otherwise, there wouldn't be so many golfers who do it! To cure yourself of slicing, there are no mistakes to correct. You just have to do what you're already doing a bit differently.
The cause of a slice is simple. Where the clubhead should be traveling through impact along a 3 o'clock to 9 o'clock path, the slice swing is traveling from 2 o'clock to 8 o'clock. Not only that, your clubface is open (facing to the right of that path), putting clockwise sidespin on the ball, which causes the ball to curve to the right. A slice is born.
To cure a slice you have to straighten out the clubhead's path and square up the clubface to that path. Let's started with the path.
Make small swings through impact, perhaps a foot long, that move straight at a "target." Gradually make longer swings, always ensuring the club moves straight at the target through impact.
You can see this when the swing speeds up by observing the club "flash" in front of you. When that flash goes in the right direction, your path is correct. Practice that movement over and over until you can make full swings with an in-line path.
To correct your clubface angle, swing the club back about three feet and stop. Without reorienting your hands, bring the club back in front of you and place the clubhead on the ground. If the face is open, you have to correct your takeaway.
If the clubface was square, continue dividing your swing into small portions and check to see if the clubface is square at each point where you stop. Investigate the entire swing, including the downswing.
When you find the place where you're opening the clubface, swing back and forth between that point and an earlier one, where the clubface was still square, doing what you have to do to keep the clubface square the whole time.
There's one final step, probably the most important one. Before you swing, direct your mind at the target. Feel the club directed toward the target with a square clubface. Feel that every movement you make, including your backswing, is directed at the target. Your mind will give your body the instructions it needs to carry out this directed, whole swing feeling.
Keep in mind that you have embarked on changing long-standing habits. Practice these changes over and over until they become your new habits.