Perhaps talking to a therapist about the root cause of your anxiety is a good place to start?
One of the obligatory, yet very effective calming methods is actually learning to breathe correctly. This is actually harder than you think and will have to constantly remind yourself to breathe deep.. pulling the air into the bottom of your lungs through "belly breathing."
I would often find myself breathing in very abbreviated, shallow breaths. I bought one of those essential oil diffusers that has the changing colored lights. I would use this as a focal point and practiced some very basic meditation techniques for several weeks and began to re-program my brain to relax. It's actually very, very effective.
Engage in physical activity, avoid food/drinks that are stimulating, practice daily meditation in an effort to relieve stress and release endorphins.
After doing this in earnest for some time, you can try the supplement "phenibut" which increases activity in the GABA neurotransmitter system.