The most common type of problem almost all golfers face at one point in time is a slice or hook. There are really only two reasons why a golf ball will curve in mid-air, and the secret to curing that slice is to find out which one is plaguing you specifically and fix it.
Who cares about distance off the tee? No golfer should even think about increasing their distance if they do not have any idea how to hit the ball straight as an arrow. I've heard many asking to get more distance, when more distance on their drive will just drive them further into the woods.
The average score improvement for people who fix their slice is between 3 and 7 strokes per round. So how do you fix this awful affliction?
First, you have to understand why a golf ball will fly left or right instead of straight. It's due to the side spin placed on the ball when you hit it. There are two types of spins: backspin and sidespin. When sidespin overcomes backspin, your ball will curve in midflight.
There are really only two reasons why your ball will receive a significant amount of sidespin, and they both have to do with your swing. The first one is because your clubface is facing to the right instead of straight ahead when it hits the ball. This is commonly referred to as having an open clubface.
The second reason is because your clubfaces comes across the ball when it strikes it. This is strictly due to an "outside-in" swing.
If you eliminate either of these two problems, your slice or hook will be dramatically reduced. Eliminate both and it'll be eliminated.