Luckily for me I'm taking classes online and don't currently have a job.. Frankly, I don't know how I'd cope with having a panic attack in a public setting. Mine get severe enough that I often can't stand/walk while it's in its peak, and I struggle to breath. I also experience dizziness, shaking, nausea/vomiting, rapid heart rate, and crying. I think if an attack hit me in a public setting in which I could not easily "escape" I would probably either try to conceal it or I'd tell someone nearby (an employee in the case of a store) and ask if there was anywhere private I could go, and then I'd maybe call a family member who could come take me home. Unfortunately I still do not possess the know-how to get myself out of one quickly or easily, and I'm afraid that feeling as though I need to hide it from those around me would just worsen the experience, especially the feeling of being separated from reality (depersonalization/derealization accompany my attacks a lot of the time).

So I guess my main suggestion would be... don't pressure yourself into appearing calm, cool or collected. Sure, it might feel embarrassing to let your panic show to others, but that feeling will probably just make it worse. Better to seek a quiet place to cope with it, and to try and calmly explain to those around you what is happening. I have actually had a mild one hit me when I went to see a play... the loud music and flashing lights were too much for me. I tried my best to stay as long as I could, but I ended up walking out and sitting in the hallway outside, practicing deep breathing and bought a water bottle to sip on. No one questioned me or looked at me overly weirdly.