Here’s a quick but logical progression from the very basic hip-opening posture called Agni Stambasana (or as my teacher John Scott somewhat jokingly calls it, Agony Stambasana), through to the more advanced Eka Pada Sirsasana. Please please don’t try to put your foot behind your head unless you’ve been taught how to do so by a qualified teacher, hopefully mid-practice, in the context of an ongoing Ashtanga practice. Just use these cues to work where it’s comfortable and beneficial for you. I hope some of the tips on Eka Pada can come in handy when you’re nice and warm and approaching the posture in the sequence of your daily practice.
And here’s the progression to Eka Pada Sirsasana: