Good golf shots begin with good posture and a good grip. Most people that top the ball have a poor concept, posture and/or grip. Most people have been told to keep their head down and arms straight…both of which have a tendency to lead to topped shots. If you want to stop striking the top of the ball, then get into an athletic setup and grip. Good golf posture resembles the same posture that you would curl weights from at the gym. Gripping the club in the fingers without too much tension will also assure that gravity works and the club can function properly.
I would also encourage someone to tee the ball up while making these changes and practice swinging through the tee. Any contact with the tee will ensure that the ball goes up in the air. This will build confidence and help lose any remaining tension. As the player gains confidence, lower the tee to the point that the golfer no longer needs the help.