When I delegate tasks, I "black-box" what I'm handing off. That means I don't hand-off tasks and then keep key pieces to myself that make it difficult for the other person to be efficient. I also clearly define what constitutes success for the particular task. That definition of success is what will come out of the black-box. 

If I'm keeping information to myself that is pertinent to the task, that may mean I don't have enough confidence yet that the specific task can be successfully accomplished by the other person. That necessary inside info is what should go into the black-box.

Maybe the person is a new contact I've never interacted with before or maybe I'm not sure that they truly have enough time. If that's the case then it's a signal to me that I need to make the black-box smaller. If the task is finished successfully then my confidence builds and I'm able to hand-off a bigger black-box task the next time around.

But if I don't black-box I can never build my trust relationship up enough to truly hand-off tasks completely.