• Stay focused.
• Stay in the pose for a few breaths, integrating its benefits.
• Slowly come out of the pose when you are ready with the same focus as you entered it;  do not let your attention wander.
• Feel the release as you come out of the pose.  You may feel a sudden gush of warm blood spreading across the whole body. 
• Take a few breaths between each side to allow the freshly oxygenated blood to flow into the tissues and for the prana to go into the various cells of the abdominal organs.   You may notice a difference in your breathing and your lungs and diaphragm may feel more alive after opening up the energetic channels. 
• Then do the other side.

When twisting, it may be helpful to visualise the colour green vibrating at the heart centre.
You may wish to repeat several times the seed mantra Yam silently in your head, or slowly and mindfully repeat an affirmation such as “I love”.

How do you know that you are doing the pose correctly?
When the rotation is done correctly, the shoulders move back and down, the top of the spine moves in, so this is an excellent stretch for correcting a rounded back.  We initiate the twist from the least moveable part of our spine, ie the lumbar area.  The limited rotation in that area is due to the position and arrangement of the facet joints.  Rotation at the hips is minimal.  The thoracic spine rotates more freely than the lumbar spine.  It is therefore important to stretch properly from the lower back and turn the spine completely as you twist rather than stick the chest out and turn the ribs and the neck.  Resist the temptation to lead with the shoulders or the head. 

It is important to understand that in a twist we are working from the inside to the outside.  On an inhalation, we create space inside the body by lifting the waist and opening the chest so that when we twist we are not forcing a twist on the spine and the internal organs by revolving only the outer body and leaving the inner body behind. 
If one is only concerned with outer alignment and ignores the inner alignment, there is a lack of integration and the pose becomes dry, brittle, dull, aggressive and potentially harmful.  When all the various parts of the inner and outer body come together, the pose becomes harmonious.

Knowing what to do in a twist is one thing, doing it correctly is a completely different matter.  You just have to watch what goes on in some yoga classes when it comes to doing Ardha Matsyendrasana.  The posture itself requires a combination of good hip flexibility, forward bending, lateral bending and twisting.  How many of us can do all these and still maintain the necessary lumbar arch to do the pose correctly and not slouch, lean forwards or sideways? How many of us can comfortably keep both buttocks on the floor?  How many of us are keeping both shoulders level and relaxed and the head in line with the spine?  How many of us have the front foot completely flat on the floor and not sitting partially on the other one?  How many of us are still breathing regularly and peacefully and enjoying the moment instead of wishing for the pose to come to an end?

Muscles used in Ardha Matsyendrasana
Back muscles:
Deep to the erector spinae lie the transversospinalis muscles which are small muscles acting directly on the spine for rotation

• rotators (deepest )
• multifidus (superficial to the rotators)
• semispinalis (superficial to the multifidus)

Torso muscles:
abdominal obliques (4):  2 internal obliques and 2 external obliques

• The 4 abdominal obliques support the lower back, the pelvis and the internal organs.  In a twist to the right for example, the left external oblique and the right internal oblique contract to rotate the torso.  Meanwhile, the right external oblique and the left internal oblique relax and lengthen.
• intercostals (internal and external which are respectively concerned with exhalation and inhalation).
• sternocleidomastoid muscles (neck muscles concerned with flexing and rotating the head).

How to breathe in a twist?
As you inhale you stretch up and as you exhale, you twist.
As you inhale, imagine the breath coming up through the floor rising through your feet, legs and trunk, expanding your chest, and moving up into your head.  Conversely, as you exhale observe your breath as it passes down from your head, through your chest and stomach, legs and feet back through the floor.
On an inhalation we bring the heaven into the earth, and on an exhalation we bring the earth into heaven and we stay perfectly poised between both.
Stay mindful and observe how the twist affects the breath.  One side is compressed, the breathing is strained due to the great compression of the lungs.

It is impossible to practice abdominal breathing when doing a twist because of the compression on the abdomen (made even worse if you are pressing the bent knee tightly against you!) and because of the compression of the lungs in the chest, diaphragmatic and  thoracic breathing are difficult too.