(nah-dee show-DAH-nah) nadi = channel shodhana cleaning, purifying
Make sure to sit in a comfortable upright, seated position. Spine nice and straight. Hands gently on your knees. You can have your legs folded, or straight in front of you if this is too hard. Keep your pelvis slightly tilted forward, you may sit on a block or bolster to support his pelvic tilt.
Vishau Mudra (left) is traditionally used. Use the dominant hand and place the fingers beside the nostrils and along the nasal creases stimulating the two nadis, Ida and Pingala Nadi Begin with blocking the right nostril, inhaling through the left nostril, next, blocking the left nostril and exhaling through the right nostril. Then, block the left nostril, inhale right, block right exhale left.
This is a difficult one to explain but very easy to demonstrate and to do, please refer to the youtube clip below to help further clarify.
Beginning the breath in through the left nostril stokes the right hemisphere of the brain creating inner calm and centering.
I am always asking my clients to perform breath work, and this one is a favourite. It can be used alone, or before your yoga practice. It is a balancing pranayama that brings equilibrium to the right and left cerebral hemispheres’ and a cleansing breath for the two dominant nadis.  Bringing ida and pingala into equilibrium is a major focus of hatha yoga. When we have attained balance of sun and moon this facilitates the awakening and rising of kundalini and we obtain higher consciousness.
Other more immediate benefits occur directly via the olfactory bulbs connection to the limbic system. This system also includes complex brain structures such as the thalamus, amygdala and the hippocampus. Functions include emotional learning, memory, social interaction, aggression, fear, anxiety, sex and there are links to addictive patterns. The olfactory bulbs connection to the limbic system helps us, through the breath, deal with stress, detox the blood, reduce anxiety and depression as well as help us deal with withdrawal symptoms. 
Please refer to this great youtube clip on how to perform nadi shodhana
So what’s stopping you? Just do this for five minutes a day and you will begin to notice the difference.
 AYA Lecture Notes, D Salerno, 2013