'...when sirsasana is mastered, the breath rate, which is normally about fifteen to twenty breaths per minute, automatically comes down',
Work towards two breaths a minute over time.
'Sirsasana should always be practiced in the morning, as is laid down by the authorities on yoga.'
'And, as a counterpose, it should be followed by an equal length of time in the practice of sarvangasana (shoulder stand)'.
'The procedure is thus to do sirsasanam for twenty-four breaths, followed by a two-minute rest in savasana. Then one should do sarvangasana for the equal number of twenty four breaths, followed by a sitting posture each as padmasana for a few breaths, until one feels normal and relaxed'.
from Srivatsa Ramaswami Yoga for the Three Stages of Life p142
Towards the end of my morning asana practice I spend few minutes in the sarvangasana preparatory postures, anapanasana, urdhva prasarita pada hastasana and dwipadapitam.
I then spend at least five minutes in sarvangasana, the first three minutes with the legs relaxed.
Then I practice for headstands for ten to twenty minutes (ten minutes minimum).
For the first five minutes I don't practice any vinyasas but try to slow my breathing towards two breaths a minute and work on engaging bandhas.
The rest of the time in headstands I spend on Vinyasas, one or more of the inverted subroutines.
Coming down from headstand I'll stay for a fem moments with my forehead on the mat, when sitting up I'll bring my head up last.
After a couple of minutes in savasana I practice another five minutes of Sarvangasana (shoulder stand), this time practising vinyasas, one or more shoulder stand subroutines
Finally I'll spend a period of time in Vajrasana, padmasana or mahamudra before moving on to my pranayama practice.
the head point of sirsasana should be the crown of the head
Control your balance with your forearms and especially your elbows
For these movements the neck and shoulders need to be relaxed and well stretched out, the hasta vinyasas in tadasana (Day 1) are a good place to start your practice.
Bend the knee towards the chest on the exhalation, straighten the leg on the inhalation.
The danger is to fall forward out of the headstand while bending the knee towards the chest, be sure to engage the opposite hip and stretch out through the full length of the leg.
The tendency is to lean the straight leg forward, imagine taking it backwards slightly to counter the pull forwards.
Don't try to bring the knee down too far on the first bend, work a little deeper on each repetition.
If necessary take an extra breath or two after each bend of the knee, adjusting the head arms and shoulders.
round your back slightly on the third bend to bring the knee lower.
Engage bandhas, uddiyana bandha, sucking in the belly will create more space allowing your to take the knee lower.
Bringing both legs to the cheat is more challenging as you don't have the trailing straight leg to act as a counterweight, round the back, again, go a little lower on each exhalation.
In Ardha-padmasana-akunchasana try to bring the leg as far into the goring as possible, shuffle the foot in a little deeper if possible.
In Ardha-padmasana-akunchasana the need to round the back slightly will be more apparent.