Descending blow contacting the ball before the ground with a good lie. That will spin the ball. To get the ball to actually backwards on the green requires all of this plus lots of club head speed.
Don't underestimate how much playing a urethane covered ball helps, too.
That said, I think that spin is generally overrated. You can play very, very good golf by playing to let the ball release. See Stan Utley's book Art of the Short Game where he talks about how he had a pretty successful PGA TOUR career by playing the release. It is important to know how much release to expect, not necessarily to know how to suck the ball back.
As others said hit down on it, more energy into that will generate more spin...If you don't take a divot the ball won't spin. The ball will aslo make a difference. Spin is over-rated - I have been screwed by spin more than I have been helped. The only time I really like it is out of a trap.
Yea spin can be a right pain, but i think the actual ball plays a big part in the spin. If i use a cheap ball, i dont get much. Maybe 2 hops and a stop
Using a good urethane covered ball it will stop dead, even short pitch/chip shots from 10 yards out. Its a pain when that happens as you normally want it to release a bit, not stop dead :P