First there is the issue of defining what a successful umpire looks like....
Edited the whole post down. I think I missed that thread, but for me, knowing the rules is #1. Not being a confrontational rear is #2 (because, and this is certainly a flaw of mine, I am much more likely to also be a confrontational rear, but if the umpire is calm and cool, it takes a LOT more for me to lose it).
My favorite umpire in our area/local rec league is a guy who I'm pretty sure blows more bang-bang plays than anybody. Others in the league talk about how terrible he is, but I love him. Because he knows all the rules. He knows our house rules (or, at least, he'll ask to clarify before a game). And if there's ever a rule-related question, he'll talk it out with you. And yep, sometimes he just gets that call at first wrong. Sucks when it happens to your team, but I feel like the game itself is safe in his hands. I'm not gonna go home feeling cheated because the umpire didn't know the rules.
Oh, #3 is "act like you want to be there." I realize this is not even an issue for so many who post here because umps who don't want to be there are likely not umping a lot of big travel tournaments, but #3 goes a long way. If I know you're trying, I'm gonna tolerate a lot before I get upset about something.