Lots. Meditation, hyponosis tapes, relaxing music, massage, aromatherapy, gentle stretching yoga routine, homeopathic medications such as calm's forte, valerian root tea and holy basil either as a plant or supplement can help relax you.
Panic Attack. If you can find a quiet place - do so. Breath in slowly ; deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer if you need to. If you haven't been assessed for your panic/ anxiety - that would be prudent. Take care.
Learn to relax your. Learn to relax your breathing. Practice when you are not having a panic attack so that when it occurs you will be prepared to use the relaxed breathing to calm yourself. At the same time remind yourself, it will pass, you are not having a heart attack or other physical problem. Therapists can teach you other relaxation techniques, too.
Yoga breathing. As you breath in through your nose, push out your stomach. Once you're comfortable with this you will start with a count of 3, mean count to 3 as you breath in, count to 3 as you hold it, count to 3 as you breath out and then count to 3 before you breath in again. Continue this for 5 mins. Your goal is to get to a count of 8 in time. This is a technique I use personally.
Try smoking (?) What! On a Health Website? I mean the breathing pattern - w/out a cigarette! Actually, many smokers benefit from the breath pattern w/out knowing the role it plays. The deep inhale, hold, and full exhale thru the lips is very good for you. It reduces BP and HR. Part of "I need a smoke! " is about this. So, don't use tobacco - but take the time of a cigarette and breathe that way whenever you want.
Panic/Anxiety Attach. Diaphragmatic breathing is a recommended technique. It is good to have a medical exam first to rule out underlying illness. You could seek psychotherapy from a clinical psychologist for a program to reduce anxiety. There are also medications to help with this. With good psychotherapy it can be possible for certain people to overcome the need for meds.