Hand signals!

The use of hand signals in umpiring is by itself not a basic necessity. One can by whistle and voice only control the game. However, using hand signals clarifies the reason for a penalty and makes it visible for people who cannot hear the umpire's decision. Mastering the hand signals also gives an umpire more authority and helps to speed up the game.

Although the official rules book shows pictures of the most common signals, some are missing. I have been trying to find a good source for hand signals. This video is the best I have come across so far.