The best way to learn is to learn on your own.
The only thing that the experts on this board can do for you is point you in the right direction. They can give you official rulings and interpretations, but those mean nothing without a solid foundation of the why's and how's.
Just as important as good equipment that you can trust, you must not cut corners where your education is concerned. A subscription to
http://www.eumpire.com is a great place to start. Finding the books and materials you hear about on the internet is also important. Get a copy of Jaksa/Roder's Rules of Professional Baseball, the NAPBL Manual is a must, keep checking Jim Evans' web site for the release of Jim Evans' Anotated, buy a copy of Carl Childress' Baseball Rules Differences, and seek out and find any and all other materials on the history of baseball rules, interpretations, or any book about the art of baseball umpiring.
I know one umpire - very good official. He bought the latest and best equipment, his uniform was always pressed with sharp creases and he always had nicely shined shoes. He looked great, like a professional.
This past season he called a runner out on appeal for failing to retouch after a foul ball. If only he had put as much effort into his education as he did his equipment and uniform, he would be the top dog around here. But that rules mistake knocked him down quite a few rungs on the officiating ladder, let me tell you.
Get your buns to as many clinics as you can. Attend camps and instructional clincs as often as possible. Keep learning for your entire life.
Once you know it all, you're in the grave.
Sincerely,
Jim Porter