Ball flight tells all:

Pulls are not draws and are the result of a downswing over the correct plane. Clubface is probably slighty closed but is usually not the main culprit. If it is a complete smother than the club face is closed and is an issue also. (fatal)

Pushes are not slices and are the result of a swing under the correct plane. If you push and slice then the clubface is open and in the mix of issues. (fatal)

Cut slices (starts left and curves right) are the result of the over the plane downswing and open clubface. Most common.

Draws are the result of an on plane swing that is on plane (slightly inside) to the ball and back inside (on plane) to follow through. Nice to watch.

You can paly very good golf with two of the above flights. Many use the cut slice very effeciently but the cut and slice part are very minimal. In fact it may look like a very straight ball flight. Draws are impressive and more difficult to achieve.

Swings over the correct plane are usually caused by a lack of lower body action in the transition. The swing is generated by the hips and shoulders alone throwing the shaft out over the correct path. ("The Sunday Spin")

Club face issues are usually due to tension and a tendency to hold off on the release of the club head through impact. Many hold the face open at set-up inadvertantly failing to use the leading edge of the sole for square alignment.