I've suffered from panic attacks since the age of 15. I'm 20 now.
The best thing that I've found that works is putting my head down, like on a table, so that it is under your heart and take deep steady breaths. Don't think about anything, just focus on breathing. If that doesn't work, I always have a paper bag handy for emergencies.
I also find drinking too much caffiene can set off an attack. As a rule, I try to avoid it.