The key to controlling anger is the ability to recognize it for what it is. If you don't even know your enemy, you'll never be more than its pawn. Understand what triggers your anger, measure its shape, its severity, and its duration before doing anything else. Only after you contain any understanding of it do you even attempt to control it.
Unfortunately, while those are good points to understanding, some modes of anger shatter the general standard. As it is, most anger experienced is not an emotion, but a physical energy that builds within a vessel, charges a space, and then explodes outward. It is this aspect of anger that cites its difficulty. A mind can hardly control its emotion without vast years of experience and a certain aptitude. Even if one mind could control all its body's emotions, what good is that ability to a localized force of nature?
Human beings are creatures very electrical in nature - all technology aside - in their control, existence, and rationalization. To move a body, one receives electrical impulses to muscle structures, the bodies feel with nerve systems that act as transmission circuits, because of the flow of iron in the blood humans create a weak electric field around them, and the brain functions on synapse explosions that push electrical patterns into waking thought and interaction. It is a perfect balance of a working electrical grid and anger is the lightning to that grid.
Whether a gradual build-up or a sudden strike, the energy will overflow a body's systems and create an effect that drives the body to levels above normal operation. Because this energy is harmful in the system it wishes to retreat through physical transferal to a siphon, whether that transferal is skin to flesh, object, air, or focused in a vocalized channel that disperses in the compounded sound waves that explode from a person's vocal cords.
This is anger in the most basic definition. Raw, brutal, untapped anger is an energy that demands the bludgeoning of an object to abate its fury. If you have the basic understanding of this feeling and can recognize what triggers the energy charge, you have a hope of achieving an aspect of control.
How to control:
We know anger is a type of energy with unknown origins. Exactly where that charge originates is not entirely decided upon, but that is not the problem. Instead, less than controlling the energy outright, it is better to learn prevention and channeling techniques.
The only way to work prevention is through experience. Without a clear indicator for what triggers energy build up, then it is pointless to try to prevent. If you have the basic triggers for your anger identified, then avoid them as best you can. Typical causes involve a tarnishing of pride, a blatant show of stupidity, infection or reflection from another's anger, or any number of triggers that set it off. If you feel like you might have the pre-sensations of charge build up, remove yourself from the source. The best control is the avoidance.
For anyone else it's too late, and you are caught in the build up of charge. Before your reaction and the transfer of the energy, you should be aware of where it resides within you. Most of the time anger can be felt charging around the chest region and behind the eyes, before it spreads through the chest and into your limbs. Immediately before this happens, you should focus everything into your arms. If you are unable to focus, that's alright, no one masters anger over night.
For re-channeling anger, it is best to push it to your arms for storage. If the anger is allowed to charge around your heart and take control of your other emotions in your head, you will regret it. The first step is to isolate the charge before it can spread. If it trapped in your arms then you'll keep a clear sense and feeling to the situation. For visual representation of the words, imagine the anger charge as a fire that starts to burn in your chest. Before that fire burns into your head and clouds your eyes with the smoke, you want to isolate the flames in your arms. This keeps the fire from burning anything but the arms, and that's okay. It tends to not receive any fuel and burns off quickly there.
In other applications anger is best converted into creative or physical energy and exhausted. Many people will work out while anger. Not only will they be more motivated to exercise, but the endorphins released from the muscles will lighten your mood. It is a double padded effect. For creative energy it may be stories, poetry, art, or something else (even an angry song) and it will help. The only channeling that does not help is the one that doesn't exist.
So for managing your anger; recognize, remember, prevent, re-channel, and covert. Remember that emotions are good to control, but this doesn't apply to energy. For better control tips, read about circuits and electric conduction, you'd be surprised but it helps in the visualization process. Anything else is up to you alone, so good luck.