All persons experiencing persistent and frequent panic attacks should consult their physicians. However, many experienced sufferers treat panic attacks with some the following methods and techniques:

Diaphragmatic Breathing or Abdominal Breathing — Breathing slowly through the nose using the diaphragm and abdomen. Do not breathe through the mouth. Focus on exhaling very slowly. This will correct or prevent an imbalance of oxygen to carbon dioxide in the blood stream.[2]
Taking anti-anxiety medication — to be used under the guidance and direction of a physician.
Staying in the Present — rather than having "what if" thoughts that are future oriented asking yourself, "what is happening now" and "how do I wish to respond to it". (Carbonell 2004)
Acceptance and Acknowledgement- accepting and acknowledging the panic attack. (Carbonell 2004)
Floating with the symptoms — allowing time to pass and floating with the symptoms rather than trying to make them better or fighting them. (Carbonell 2004)
Coping Statements — repeated as part of an internal monologue
"No one has ever died from an anxiety attack."
"I will let my body do its thing. This will pass."
"I can be anxious and still deal with this situation."
"This does not feel great, but I can deal with it".[2]
"I am frightened of being frightened, therefore if I stop worrying about being frightened, then I have nothing to be scared of."
Talking with a supportive person — someone who has experienced true panic attacks personally; someone who is highly trained in treating panic attacks; loved ones who can offer support and comfort.

http://en.wikipedia.org/wiki/Panic_attack