Deep Breathing is probably the most important action one can take toward reducing anxiety. It's also the suggestion that get's the most eye rolling from my clients. Though it does seem simplistic I can't stress how important it is to add some deep breathing into your routine. I have a brief description written out here and below there are some videos I found on the internet that are quick descriptions on how to breathe effectively.
How it works:
Begin by noticing your breath. You want to take note of both the rate at which you normally breathe and how deeply you inhale and exhale.
Now begin to both slow the rate of your breath, and increase the range of your inhaling and exhaling.
I suggest that you count each breath down from five and have each breath slower than the previous one until you reach one. The rate you've now established should not be so slow that you are gasping for air but significantly slower than your normal rate of breathing.
Continue for an extended period of time. I'd suggest at least five minutes.
Why It Works:
Deep breathing can help decrease your heart rate.
It sends a message to the brain to decrease anxiety.
It can also decrease negative thoughts.
Deep breathing keeps all the organs in the body running smoothly.
Diaphragmatic Breathing Video
This is a good description of Diaphragmatic Breathing.
How to Deep Breathe
Here's a short video I found on how to deep breath.
Different style of breathing but still effective.