Espola,
You are usually very helpful to those parents who lack your experience and wisdom.
The criteria is not obvious to me. Please share your knowledge. Seriously, many folks here are trying to learn in order to help our kids reach their goals. Your post has a chilling effect on asking "obvious " questions.
The best way to evaluate a player is in a game, but sometimes players go a long time without any time on the ball, which can limit what you can see. Personally, I look for balanced left/right ability, ability to trap a difficult ball, and apparent knowledge of where to go without the ball. The world is full of hot shooters, but playmakers are rare.