Starting position

Hold the yo-yo in such a way in the hand, that the stringcoil from above leads to your middle finger.

Yo-Yo Trick Sleeper start position

Throw the yo-yo loosely from the wrist, but nevertheless with momentum downward. 
As the yo-yo is down, you turn the hand (palm is now down), in order to catch the yo-yo.
For yo-yos without a centrifugal clutch a small jerk is needed to return the yo-yo.
So that a yo-yo with a centrifugal clutch sleeps at the end of the string, strength is not crucial.  The optimal momentum (rotation) and an easy giving way are important for the moment, as the yo-yo arrives the end("dead" point).  

The sleeper is the basictrick for stringtricks.

Yo-Yo Trick Sleeper 1
Yo-Yo Trick Sleeper 2
Yo-Yo Trick Sleeper 3!