Letting Off Steam
Let off some steam first. Sometimes anger leads to an internal clarity or focus that actually moves the body into positive and beneficial action - acts of bravery are the result of such focus. More often, however, anger can cloud the brain, making rationality fuzzy. It may provoke a desire for striking back with violence, more anger, or a plot for revenge.
If you're still hot" about the situation that has provoked your anger, it is best not to try to negotiate with your perceived "attacker" immediately, if it can be avoided. In many more situations than we might imagine, leaving the scene, at least temporarily, is a viable and valuable option. It is next to impossible, while still in the throes of an anger episode, to speak or listen to someone else without offensive or defensive overtones or blockages. Letting off some steam is an important intermediate step. It's certainly better than swallowing and internalizing the anger, turning it into poison or violence to yourself. A deep, rich, full breath (or two or three) may be all you need to gain a bit of perspective and to soften a tone that would otherwise provoke the other person even more.
If you are indoors, stepping outside for a change of scenery and some fresh air, or merely opening a window and looking at the sky or the trees, for instance, can be enough to alter your mood and maybe the mood in the room. If you don't have to face the other person right away, you can take a fast walk around the block, take a bath, listen to some music, stroke your cat. Perhaps you need to beat on your bed with a tennis racket, park your car on a back road and yell, or conduct a mock argument or "negativity" session with a friend. Discharging some of the energy first may clear your head and makes it easier to identify the problem. Monitor for yourself whether catharsis (yelling or beating on something) is helping you to get clear or not. If it does, use it. If it builds more anger or fear or frustration, don't do it. A hard game of tennis or other aerobic activity, or simply talking to a tree or a willing friend, are helpful ways to deal with the raw edge of anger.