A slice seems almost impossible to figure out if you don't have proper instruction. The cause, which is known as a shoulder drop, is often illusive to beginners. If you drop your back shoulder when you hit the ball, you open up the club face, sending the ball off in the wrong direction. Training yourself to stop dropping your shoulder is easier said than done, but it is possible.
Oftentimes, golfers with a big slice give up on trying to correct their shoulder and find ways to compensate instead. You can apply a quick fix that doesn't solve the issue but may keep you closer to the fairway. If you're right-handed, address the ball so that you are facing down the left-hand side of the fairway. Depending on how hard you slice the ball, adjust it more or less.
A surefire cure for the common slice is a simple visual. Imagine railroad tracks running away from your ball toward the hole, or wherever you want the ball to go. Stand on one "track" and imagine that your ball is sitting on the other track. The key is to keep the club head inside the track during your backswing and your follow-through. Your body will be better aligned, preventing you from opening up and slicing.