It might be easier at first to practice while lying down. If this isn't possible, do the exercise sitting in a chair with both feet on the floor. Place one hand on your stomach and one on your upper chest. The goal here is to inhale in a way that only moves your lower hand, while your upper hand stays still. You might just do this for a few breaths in an exaggerated way to get a feel for it. The reason it's important to breath from your abdomen is because you will be able to fill up your lungs more completely. This is a more efficient way to breathe.
OK. Get comfortable lying down or sitting up in a chair. Place one hand on your stomach and one on your upper chest. Remember, you only want your lower hand to move during this exercise. It is also helpful to inhale through your nose and exhale through your mouth. This way you can concentrate on the cool refreshing air coming in and the warm air leaving your body.
The more you practice each day, the faster you will be able to "reset" the pace of your breath, and you will be breathing more from your abdomen than you do from your chest. After a few times practicing with your hands on your stomach and chest, you won't need to do this anymore - unless you want to. Then, you can practice anytime you have "down" time - like when you are waiting for class to begin, when you are watching TV, or you're reading, or while you are waiting in a line... anytime you can, practice this easy exercise. Some people like to remind themselves every hour on the hour to check their breathing... slowing it down if they need to. Do whatever works for you. Soon you'll be breathing much easier and you'll notice how much your anxiety has decreased.
A very small proportion of people, when they first attempt to enter a state of deep relaxation, have a paradoxical reaction and feel extremely uneasy and anxious, and may have increased respiration and racing thoughts. If this happens to you, be assured that this is not abnormal! If the more “quiet” forms of relaxation leave you feeling anxious, begin your relaxation training with progressive muscle relaxation.