i also suffer from frequent panic attacks!
Mine come on when i least expect it,and for no apparent reason.
I tend to just feel extreamly paniced,frighted,hard to breathe and all i want to do is just to jun outside and get "cool" i normal just have to move out of the room and stick my head out of the window and drink cool water slowly,not fast as i found it worsend the situation.
If you can feel one comming on though just take deap beathes and think about somthing else,do something else anything...i know its hard at the time to think about anything else but if you remove your self from the "panic" situation it may help,as it does for me!
take care and keep calm!
x