I get this one a lot and my common answer is you need to learn how to swing down on the ball. The goal is to have proper ball then turf contact. The problem is with many players they tend to flip the club at the ball or try and lift the ball up in the air. Neither one of these techniques is going to put backspin on the ball.

Set up with your weight primarily on your lead foot, and pretty much leave it in that position. There really isn’t much weight shift in this shot.

In the beginning play the ball back in you stance, closer to your trail foot. Make practice swings seeing the club bottom out on the target side of the ball. If doing properly your club should be traveling on a downward angle.
Play the shot with a lofted club, sand wedge or lob wedge would be preferred. By swinging down the grooves of your wedge can dig in on the ball and help produce some back spin.

Here are couple of things that can also help;
-Make sure that the grooves on your wedges are clean.
-If your wedges are real old, that probably means your grooves are pretty dull.
-Golf balls with softer covers (urethane) usually do much better. The grooves in your wedges grab the softer cover and help to produce more backspin.