This is one of the easiest breathing exercises you can do.
Sit comfortably on the floor in a cross-legged pose, keeping the spine straight. If you are not comfy in this pose, sit upright on the front end of a chair with your feet flat on the floor.
Close the right nostril with your right thumb and inhale through the left nostril. Inhale into your belly, not into your chest.
After inhaling, hold your breath for just a moment.
Exhale through your right nostril while closing the left with the ring and little finger on your right hand.
Repeat steps 1 to 3, but this time start by inhaling through the right nostril (while you close the left nostril with your ring and little fingers).
Practice this pranayama for 5-10 minutes.
Information from: The Complete Book of Ayurvedic Home Remedies,Vasant Lad