Most umpires do work hard out there. I'm more than happy to give credit where credit is due. They show up early, they look sharp, keep control of the game and know the rules. That's all any coach, player or fan can ask for.
That being said, it's the umpires who show up looking like a bag of rubber clown noses that make the rest look bad. Unfortunately, those are the umpires that are remembered. Here are a few things that IMHO "make or break" an umpire.
Appearance - Look official and you are considered "official". That means wear a uniform that is clean and FITS. Be clean shaven/well kept and have a smile on your face. Remember, you're being paid for the best seat in the house.
Professionalism - Be courteous and respectful to coaches. Even if they are not in return. This includes not making any comment come across as condescending.
Intelligence - Know the rules. So often are there times when the umpire simply doesn't know the rule. This simple fact is the quintessential difference between a good and bad umpire.
Hustle - Be in the proper position to make the call. No one expects you to be able to run a 4.3. At the same time, there should be a very visible effort to be in the correct location to make the correct call. You can be in position, miss a call and no one will say a word. Be out of position and make the correct call and the line for complaints will form on your right.
Etiquette - Everyone knows that there is an etiquette to "arguing" a call. Don't get "butt hurt" if someone goes jogging by between innings (without giving the appearance that they are talking to you or saying anything for that matter) and says something (that only you can hear) about a call. As long as it's a respectful comment, it's not personal. It's actually a "professional" way of saying their piece without trying to "show you up".
Understand these things few things and you will go a long way towards being treated a lot better in the high school baseball world. Don't, and you will all continue to have tomatoes thrown at you.