One important consideration with every golf swing -- and a clear difference between top players and most amateurs -- is the position of the hands at impact.
With a good player, the hands are even with their left (lead) leg and ahead of the ball at impact. Amateurs tend to have their hands at the center of the body and often behind the ball.
To fix it, here is a simple drill:
-- Start by placing the hands in the proper impact position.
-- Using perhaps an 8-iron, start hitting low chip shots, always making sure the hands are in the proper position at impact.
-- Slowly grow the backswing and follow-through, but never go beyond a point from which you cannot return to the proper impact position.