bobmac
Major Champion
Decide firstly whether you want to play a low shot, a medium shot or a high shot.
This will be dictated by the lie, the slopes, the amount of green you have to play with, the softness/hardness of the green, obstacles, wind etc etc.
Once you have decided on the shot and a club, look for a spot where you want to land the ball and have a few swings feeling how long the backswing and through swing need to be for the length of shot.
Then commit to the shot.
If the backswing is too long, you will more than likely decelerate into the ball causing the duff.
So keep the backswing a little shorter which will allow you to be positive with the downswing.
And practice

This will be dictated by the lie, the slopes, the amount of green you have to play with, the softness/hardness of the green, obstacles, wind etc etc.
Once you have decided on the shot and a club, look for a spot where you want to land the ball and have a few swings feeling how long the backswing and through swing need to be for the length of shot.
Then commit to the shot.
If the backswing is too long, you will more than likely decelerate into the ball causing the duff.
So keep the backswing a little shorter which will allow you to be positive with the downswing.
And practice