The most effective measure is to enforce the rules consistently, courteously, and firmly. Show that you care and are engaged and on duty at all times, including between innings.
I enforce the time limit on warmup pitches. If a pitcher dilly-dallies about his warm-up pitches, I'll tell the catcher "two more!" a pitch or two before he expects it. Then, as he receives those pitches, I ask him to advise the pitcher that if he wants his full allotment of warmup pitches, he needs to get to the mound promptly and throw them. Catchers are smart: enforce the rule once, and they remember it the whole game.
Also, when I shoo players back into the box, I give them a condensed summary of the rule--"keep one foot in unless you swing, the ball hits the ground, or the action gives you a reason."
In youth ball, I'll discuss shagging fouls, staying in the box, replacement baseballs and other speed of games issues at the plate conference. However, I do not mention such things at the plate conference with high school coaches because they are entitled to the respect of an umpire who grants the presumption that they and their players already know the rhythms of the game.