You are slicing for an unknown reason. Your shoulders might be more open to the target than your hips at contact or you swing on an out-to-in path, causing contact off of the center of the clubface, resulting in a slice.
You need accuracy on an elevated tee box or in windy conditions.
You are about to tee up but notice that the fairway is very narrow or there is brush obstructing a clear shot.
You want to gain a powerful swing by learning the New X-factor technique, but are confused about the conflicting styles.
You need to hit further or just want to lean how the pros accomplish the X-factor. Overturning your hips causes a reverse pivot at the top of your swing, therefore placing too much weight onto your forward foot at the wrong point in your swing, leading to consistency problems.
You have a severe hook or a snap hook. As soon as the ball leaves the clubface, you notice that it curves hard from right to left and it quickly loses loft. As you make contact with the ball, the clubface will point to the left of your intended target.
Decreased flexibility can prevent proper hip rotation and therefore power, causing you to sway during your backswing. This is a very common problem for senior golfers because their muscles tighten as they age, inhibiting a proper turn for a full swing.
You want to learn how to rip your drives or just improve your driving technique.
You are on a narrow fairway or it is very windy so you need to keep the ball lower.
You are losing power in your swing, but are not sure why. A common culprit is poor hip position and the associated swing path. A swing that is too steep will cause your forward hip to drop and results in a loss of power. Conversely, an incorrect hip angle will tend to cause a steeper swing.