Just carry a big hairbrush around and tell people that you will start swinging it if they don't stop messing with you. It works for me. Other than that, I pray, a lot (that I don't swing it someone). I yell when I'm in the car. Sometimes the windows are rolled up, sometimes not. I exercise to work out my pent up frustration. I walk, go for a swim, dance, punch a pillow, sing to a song on the radio really loudly. If you are old enough, then get a someone who enjoys having their *** kicked. Believe it or not, there are people out there that really like this. Take it out on them. If you really do a good job, sometimes they'll pay you. Crazy, but true. You will have to try a bunch of different things to see what works for you.
Meditation, yoga, exercise. Research shows it helps with negative emotions and the stress it can put on the body. Sooner you learn to deal with it the better. I am starting late, but at least I've started.
Reading helps a great deal
I use to get angry a lot also, at life, at things, at people.. rather miserable time to be honest given the world can be pretty ****** if you look at it the right way.
This was until I started asking myself why these things would make me angry, and what I could do about it..
In the end, I now brush off things that I can't change or get out of my life easily, and everything else I action, and shove it all out. No need to get angry now since all end soon.. The quicker you move on, the less likely you are to get angry.
It's also had the beneficial effect of allowing me to see the bright side of things, and reinforced the fact that the world can be pretty bloody stunning if you look at it the right way.