I didnt read all of the replies....( but I'm being lazy today, forgive me ) so perhaps another has mentioned this....
From my experience, when you are talking to players during the game while the ball is live.....using one word followed with your whistle if needed is a great option.
" Lane " - " hands " - " EASY! " ( post play )
One reason this option works well is you avoid the potential " must whistle " between words
One of my personal favorites is prior to throw in and things are getting testy......hold onto the ball and look at the players with a smile and a " what the heck are you two doing? " look..... hahha..... but the situation must be appropriate.
my 2 cents