Responding to the below quotes:
Agree that a good umpire needs to be able to be able to manage a game effectivly. This can't be given or taught right away, it takes experience and time to learn. That being said, I do think that training by an experienced and competant umpire is important for new umpires and particurally youth umpires. Learning the proper mechanics early before getting into bad habits is necessary to both be effective and extend the "life of an umpire" behind the plate preventing injuries. That being said, it is my opinion. But yes, "field/game management" is one of the most important skills along with proper mechanics and making the right calls. Similar to @mstaylor said, I started as a teenager, starting on the bases for a number of years after aging out of LL. Went into umpiring instead of Babe Ruth or HS ball.
I agree personally that as Harry Wendelstedt was known for, it is important to let coaches ask questions and say their piece, but when it is time to go it is time to go. I also like and agree with the quote "Its the players job to play, the coaches job to coach, and the umpires job to umpire."