This is one of my favorite ways to calm and center.  It's a simple and powerful breathing technique by Dr. Andrew Weil.
With your tongue to the roof of your mouth, breath out.  Breathe in for 4 counts.  Hold for 7 counts.  Breathe out for 8 counts.  Repeat this sequence 4 times.
Use it in the morning and the evening and anytime throughout the day when you feel you need it.