For me, I get kind of hyper aware of my surroundings, start feeling "off", usually start pacing because I KNOW what is coming, I start sweating, and then I get horrible pain in a band around my chest, usually radiating from my back - just under where my bra strap is. Then in comes my brain telling me that this is it, I'm dying, I should go to the hospital, I'm getting my husband to pound my back where it hurts (it feels better that way for some reason) and then....usually within 15 minutes ALL symptoms are gone!! I find that if I repeat some affirmations during the attack (I'm fine, I'm not dying, it's not real, I've been tested and there is nothing wrong with me, this will be over soon ect) and chug a big glass of water it helps.
It sucks, and every time it is still hard to deal with, but my husband knows the drill by now and is a huge help to me, plus I have been checked out many times - EKGs, ultrasounds, blood work, ect so I KNOW that it's not fatal, and that helps a LOT.
There are tons of different symptoms though, it can be totally different for everyone. I'm in Canada, so it doesn't cost me anything to go to Emerg if I am really freaking out and get the tests that ease my mind. If you can, go if you have an attack, the reassurance realllly helped me
Good luck!