On the youth side, very few kids show an aptitude for catching.
Some have one or more of the major traits: leader, game smart, strong arm, quick feet, efficient throwing motion, framing, blocking, and game calling.
Some of these can be worked on more easily than others. Pick your battles as far as investing time on certain guys.
I would argue that if a candidate possesses the first three...a strong arm, game smarts, and leadership qualities that I can vastly improve everything else with some hard work.
Without those three...you are inevitably wasting your time.