[Graham]

Just to expand a little on Martin's answer, basically on that type of spin the trick is for the follower to leave her hand extended at around waist level as she comes round to face on the rotation where she wants to reconnect (if she's doing multiple spins it won't be extended until the last rotation, or at least what she's intending to be the last rotation). Since you're basically waiting with your hand in the right place, as she comes round her hand just slaps neatly into yours and you carry on dancing. The leader's skill is in correctly judging the height at which the follower's hand will come round. The follower's skill is in extending her hand at the appropriate time and at a consistent height.