Below are the things that have helped me with my anxiety and panic attacks, in order of how dramatically they seem to have helped me with preventing and coping with anxiety (the most helpful to the least).
Seek out appropriate medications. See psychiatrist. Even if one medication does not work, you can try different ones. I tried two or three different medications before my psychiatrist and I found one that really helped me.
Switch from regular coffee to decaf coffee.
Practice breathing exercises, such as belly breathing (diaphragmatic breathing) and breath control. The Android app Prana Breathing is very helpful for practicing and learning breath control; I use it fairly often, especially when I want to calm down or relax — not just when I'm anxious.