Standing - crouching - behind the very point of the plate, from which all of fair ground vectors out, the home plate umpire has the best single view of all the action. From just outside the lines, he has the commanding position and a central role in all that unfolds. As players and fans, we all know the profound effect umpiring can have on any given contest; I'd maintain that a pitcher's chances of having a quality outing are entirely dependent upon what Mister Umpire is thinking and seeing and calling on that particular day. A 1-0 game almost always features an ump with a generous strike zone (generous, that is, to the pitchers) while an 17-11 bloodbath almost always derives from him squeezing the pitchers and forcing them to throw the ball right into the walloping zone - or else walk a conga line.
In recent years we've seen MLB umpires hand most of their power (which had gotten considerable) back to the commish. A union leader took them to the edge, and a portion of his rank and file followed him right off the cliff. There was considerable justice in that. Individuals within the collective had become drunk with their own power and insisted on personalizing the game to their own individual styles, somehow missing the point that we fans weren't there to watch them style, or to call "my strike zone," but to call the real strike zone per the real rules, and do so invisibly. Oh well - they learned. Things seem better now; with some retraining and refocusing on what the rule book says, the strike zone has rotated back 90 degrees and no longer lies sideways, with balls six inches outside called strikes and strikes above the belt called balls. The game is better when batters have to hit the high strike and pitchers have to paint the corners with a brush, not a spray can.
As a pitcher, working Mister Umpire is tricky business. At a basic level, you have to establish your pitches and show you can hit spots to get an umpire to work with you. You don't want a lot of face time with Mister Umpire; it's best, really, that he wears that mask most of the time. You have to play with your body, not pray with your stare. It's best to regard Mister Umpire Sir as God, and not demonstrate even a hint of frustration with any specific call. It's a matter of accepting that once a strike/ball call is made, it ain't gonna change. Best to move on and demonstrate with the next pitch that you can hit at least an inch of the zone - that you can get a seam over it. Most umpires want to call strikes, and if you can dance with them to find a mutual rock and rhythm they will work with you. But they hate it when a pitcher whines about this call and that; the strike zone tends to shrink, not grow, as a result.
Still the same, there are limits to what you can suffer silently, and sometimes the logic of squeaky wheel getting grease can work. Good coaches work that angle from the bench, and try to keep the ump's glare off their pitcher and on them. The sideways pressure can sometimes work, making the ump want to call a strike. Still, it's up to the pitcher to hit spots that at least resemble strikes.
Hitters also work the ump. First at-bat, you'll often see what looks like a friendly greeting, ain't this a beautiful day, sir. Good umps are neutral to that, and most have little patience for a batter's complaints pitch after pitch. The shrinking strike zone can also grow rather suddenly, and one "bad" call can change the entire at-bat for a batter prone to distraction. Smart hitters clam up, take their hacks, and hope Mister Umpire can just be consistent so that the same pitch called ball two is not then called strike three.
Hostility seldom helps, from either side of the equation. Pretending that God is calling this game is most often the best practice. And if it turns out to be Satan instead, well it's best not to mess with the devil either, ain't it?