There are many ways to practice yin, there is no absolute one way. These are ways/concepts that are helpful for me and I hope assist you as well.
When to practice:
Anatomically we are targeting deeper connective tissue. Some practitioners believe early in the day is ideal, as your muscle are cool, I personally prefer after a light/or vigorous asana or at the end of my day to help wind down for sleep.
Playing with your edge:
When you enter a yin pose it is ideal to go to a depth where you begin to feel sensation or resistance in the body. Don't go as deeply as you can immediately, rather ease in. After 30 second to a minute you can go deeper after you give your body time to acclimate. The body gently opens and invites you deeper into the pose when supported in this way. Drop your expectation on how the pose should look, it's really about how it feels. Use as many props as helps your body to feel comfortable with the uncomfortable. We encourage muscle to melt away from bone allowing time and gravity to evolve the pose rather than effort. If you are hyper mobile you can play with subtle muscle engagement to protect your joints and ideally only go to 30-40 % of your end range.
Sensations we are looking for:
Stretching, squeezing, elongation, twisting or dull ache. We are very mindful to not have: Pain, sharp, burning, electric shooting, numbness or tingling. Those are signs to find an alternative variation, use more props or to take rest instead.
Resolve to be still.
Once you find an appropriate edge, it's time to settle into the pose without moving. Stillness in the body means the muscle aren't activated and the therapeutic stress can go to the yin tissues appropriately. Stillness in the breath can be very different from one practitioner to the next. Some prefer to have a longer exhale for the first few posture to help settle into the practice (option to use counting eg. inhale to 4 exhale to 5), while other enjoy a light ujjayi breath or a completely unforced breath. Stillness in the mind is greatly helped by calming our breathing. Keeping our body still can help calm the breath so these 3 elements are closely linked.
Hold for a time:
For some practitioners 1 min holds are ideal while others prefer 3 min , 5 min or up to 20 min postures. It is the slow gentle traction over a longer period of time that benefits yin tissues.
Everybody is unique and so are their tissues. The appropriate stress comes down to the tolerance level of that tissue. We stress tissue then rest to allow it to recover. Many practitioners find its not depth of the posture but rather the longer holding time that offer the most benefit.
Starting your practice by reminding yourself of why can be helpful. For some it is to enhance their health and well-being, to assist aging more gracefully, to slow down or to feel more connected with your body the reasons are numerous.
Meditation or mindful focus:
Set the foundations for equanimity. Noticing how the body is without judgement.
Either sitting or laying down notice the room around you, the sounds, the scents, the temperature.
Focus on the quality and depth the breath without changing it initially.
Allow your awareness to settle into the lower belly, observe sensations here. Start to deepen the breath having a longer exhale then inhale and notice how this changes this area of the body,
Move the focus to the level of the heart and check in with the state of emotions.
Shift the awareness to the point between the eyes, observe thoughts that arise. Without trying to stop them simply watch them come and go.
If the mind is active it is helpful to give it a task like focusing on the lower belly and longer exhale then inhale for the first few postures before allowing the breath to be natural and broadening the focus to sensation found in the body, thoughts as they arise and their changing nature.
Wishing you lovely yin practises.