The principles of the practise
There are three over arching principles applied to the practise of yin yoga:
1) Come into the pose (or shape) to an appropriate depth (your edge)
2) Resolve to remain still
3) Hold for sometime (traditionally 3-5 minutes in most cases)
I like to add a 4th
4) Come out with care (we often don't pay attention to places in-between doing, but these are important, not to mention there will be some fragility created in the tissues having held the pose)
And then I add an over arching principle - PAY ATTENTION!
This is vital to enable you to find the edge, to notice when that edge shifts and to keep the mindful focus of the practise alive.
Yoga (yin or other styles!) is the art of listening to the body and responding - to do this you must pay attention!
Watch video and use these over arching principles to inform your own practise and guide your teaching.