Qualifications
You might be the coolest cat in town, but coolness alone can't make you Emperor Umpire of the Imperial Baseball League. Like any other job, you're going to need schoolin', trainin', and a ton of practicin' before you can put on that coveted uniform and rule the field with an iron fist.
First, like most jobs, you'll need a high school diploma or G.E.D. (source). If you don't have that yet, and aren't working towards it, we suggest you stop reading right now. Stop. Right. Now. And go do that.
After that's all done and your parents are all proud and junk, you're going to need to attend one of the two professional umpiring schools in the United States whose curriculum has been approved by Major League Baseball.
Check out the Minor League Baseball Umpire Training Academy and the Harry Wendelstedt School for Umpires (source). Each training program lasts four to five weeks in January or February every year. Why January and February? It's the off-season.
Did you find the program that's the best fit for you? Hopefully you graduated in the top of your class and impressed a few people. Now you're ready for the big leagues. New York Yankees, here you come.
Just kidding.
Sorry.
You'll actually first be placed in a rookie and short-season Class-A league, and work your way up from there until the glorious, wondrous day when you finally get "The Call" for the Majors.
What can speed that process up? What else should umpires have? The baseball deciders dictate that you should have a "reasonable" body weight, twenty/twenty vision (with or without glasses, for all you smart-looking four-eyes out there), some athletic ability, and a good driving record.
You have all that? That's wonderful. At the very least, you can be thankful for your good health, vision, and physique. Shall we move on to the intangibles?
You'll need good communication skills. A lot of the job is talking with coaches, players, other umpires, and MLB bureaucrats. Sadly, it seems no job is safe from networking. A sharp eye will be helpful too, because you'll be making split-second decisions. You can blink...we just wouldn't recommend doing it too often.
Finally, you've got to be able to maintain your cool under pressure. Not just because the outcome depends very much on you getting the calls right; even if you're perfect, angry coaches, fans, and players will let you know when they disagree. You've got to be able to take it without breaking down into a puddle of emotions behind home plate. After all, there's no crying in...well, you know.