Hi TJ,
The very basic thing to do is to make sure that you take care of yourself by getting adequate sleep, healthful nutrition, and daily exercise. ADD/anxiety disorder has a very low to no tolerance for neglecting any of these three areas.
In his books, "Healing ADD" and "Healing the Hardware of the Soul", Dr. Daniel Amen outlines techniques to use to cope with anxiety and depression. One chapter is entitled "Killing ADD ANTs (automatic negative thoughts). He also uses biofeedback, self-hypnotic reprogramming, counseling, relaxation techniques, meditation, and medication in his practice.
Are you presently taking medication? Taking only a stimulant (ritalin, adderall, etc.) for ADD can aggravate your anxiety. Usually, a stimulant with an anti-depressant or anti-anxiety medication is needed. Check with your doctor.
I encourage you to check out Dr. Amen's website at brainplace.com. Click on "anxiety" in the menu on the left-hand side. His entire website contains a wealth of information on ADD.
Blessings, momo